diff --git a/lib/namespaced.php b/lib/namespaced.php
index eab91b64..93864ba5 100644
--- a/lib/namespaced.php
+++ b/lib/namespaced.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 require_once dirname(dirname(__FILE__)) . '/autoload.php';
 
diff --git a/lib/php72compat_const.php b/lib/php72compat_const.php
index baa0f1e1..5a876a67 100644
--- a/lib/php72compat_const.php
+++ b/lib/php72compat_const.php
@@ -1,5 +1,5 @@
 <?php
-
+declare(strict_types=1);
 const SODIUM_LIBRARY_MAJOR_VERSION = 9;
 const SODIUM_LIBRARY_MINOR_VERSION = 1;
 const SODIUM_LIBRARY_VERSION = '1.0.8';
diff --git a/lib/php84compat_const.php b/lib/php84compat_const.php
index 3a9895fa..7f508b62 100644
--- a/lib/php84compat_const.php
+++ b/lib/php84compat_const.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 const SODIUM_CRYPTO_AEAD_AEGIS128L_KEYBYTES = 16;
 const SODIUM_CRYPTO_AEAD_AEGIS128L_NSECBYTES = 0;
 const SODIUM_CRYPTO_AEAD_AEGIS128L_NPUBBYTES = 32;
diff --git a/src/Compat.php b/src/Compat.php
index fe12c530..6c020a98 100644
--- a/src/Compat.php
+++ b/src/Compat.php
@@ -3219,6 +3219,7 @@ public static function pad(
             $k = $unpadded_len;
             for ($j = 0; $j <= $xpadded_len; ++$j) {
                 $i = (int) $i;
+                /** @psalm-suppress RedundantCast */
                 $k = (int) $k;
                 if ($j >= $unpadded_len) {
                     $padded[$j] = "\0";
diff --git a/src/Core/AEGIS/State128L.php b/src/Core/AEGIS/State128L.php
index c5c4585c..3e33cf74 100644
--- a/src/Core/AEGIS/State128L.php
+++ b/src/Core/AEGIS/State128L.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AEGIS_State128L', false)) {
     return;
diff --git a/src/Core/AEGIS/State256.php b/src/Core/AEGIS/State256.php
index 0bf40526..30cb5ef8 100644
--- a/src/Core/AEGIS/State256.php
+++ b/src/Core/AEGIS/State256.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AEGIS_State256', false)) {
     return;
diff --git a/src/Core/AEGIS128L.php b/src/Core/AEGIS128L.php
index 7198cd79..bf38c050 100644
--- a/src/Core/AEGIS128L.php
+++ b/src/Core/AEGIS128L.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (!defined('SODIUM_COMPAT_AEGIS_C0')) {
     define('SODIUM_COMPAT_AEGIS_C0', "\x00\x01\x01\x02\x03\x05\x08\x0d\x15\x22\x37\x59\x90\xe9\x79\x62");
diff --git a/src/Core/AEGIS256.php b/src/Core/AEGIS256.php
index df65e327..c2d9bb00 100644
--- a/src/Core/AEGIS256.php
+++ b/src/Core/AEGIS256.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (!defined('SODIUM_COMPAT_AEGIS_C0')) {
     define('SODIUM_COMPAT_AEGIS_C0', "\x00\x01\x01\x02\x03\x05\x08\x0d\x15\x22\x37\x59\x90\xe9\x79\x62");
diff --git a/src/Core/AES.php b/src/Core/AES.php
index daa7e62d..6fd33433 100644
--- a/src/Core/AES.php
+++ b/src/Core/AES.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AES', false)) {
     return;
@@ -271,6 +272,7 @@ public static function keySchedule(
         for ($i = $nk, $j = 0, $k = 0; $i < $nkf; ++$i) {
             if ($j === 0) {
                 $tmp = (($tmp & 0xff) << 24) | ($tmp >> 8);
+                /** @psalm-suppress InvalidArrayOffset */
                 $tmp = (self::subWord($tmp) ^ self::Rcon[$k]) & self::U32_MAX;
             } elseif ($nk > 6 && $j === 4) {
                 $tmp = self::subWord($tmp);
diff --git a/src/Core/AES/Block.php b/src/Core/AES/Block.php
index ac5524bb..ae39b82e 100644
--- a/src/Core/AES/Block.php
+++ b/src/Core/AES/Block.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AES_Block', false)) {
     return;
@@ -6,6 +7,8 @@
 
 /**
  * @internal This should only be used by sodium_compat
+ *
+ * @psalm-suppress MissingTemplateParam
  */
 class ParagonIE_Sodium_Core_AES_Block extends SplFixedArray
 {
diff --git a/src/Core/AES/Expanded.php b/src/Core/AES/Expanded.php
index 5e53b219..053b5601 100644
--- a/src/Core/AES/Expanded.php
+++ b/src/Core/AES/Expanded.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AES_Expanded', false)) {
     return;
diff --git a/src/Core/AES/KeySchedule.php b/src/Core/AES/KeySchedule.php
index d08f6026..ade8556f 100644
--- a/src/Core/AES/KeySchedule.php
+++ b/src/Core/AES/KeySchedule.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_AES_KeySchedule', false)) {
     return;
diff --git a/src/Core/BLAKE2b.php b/src/Core/BLAKE2b.php
index 965598fc..0e569621 100644
--- a/src/Core/BLAKE2b.php
+++ b/src/Core/BLAKE2b.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_BLAKE2b', false)) {
     return;
@@ -450,7 +451,7 @@ public static function update(SplFixedArray $ctx, SplFixedArray $p, int $plen):
             if ($plen > $fill) {
                 # memcpy( S->buf + left, in, fill ); /* Fill buffer */
                 for ($i = $fill; $i--;) {
-                    $ctx[3][$i + $left] = $p[$i + $offset];
+                    $ctx[3][$i + $left] = $p[(int) ($i + $offset)];
                 }
 
                 # S->buflen += fill;
@@ -477,7 +478,7 @@ public static function update(SplFixedArray $ctx, SplFixedArray $p, int $plen):
                 $plen -= $fill;
             } else {
                 for ($i = $plen; $i--;) {
-                    $ctx[3][$i + $left] = $p[$i + $offset];
+                    $ctx[3][$i + $left] = $p[(int) ($i + $offset)];
                 }
                 $ctx[4] += $plen;
                 $offset += $plen;
diff --git a/src/Core/Base64/Original.php b/src/Core/Base64/Original.php
index ce6daa09..683e8f5f 100644
--- a/src/Core/Base64/Original.php
+++ b/src/Core/Base64/Original.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 /**
  * Class ParagonIE_Sodium_Core_Base64
diff --git a/src/Core/Base64/UrlSafe.php b/src/Core/Base64/UrlSafe.php
index dd9fd13e..04733aa2 100644
--- a/src/Core/Base64/UrlSafe.php
+++ b/src/Core/Base64/UrlSafe.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 /**
  * Class ParagonIE_Sodium_Core_Base64UrlSafe
diff --git a/src/Core/ChaCha20.php b/src/Core/ChaCha20.php
index 13bf9276..0b8113fe 100644
--- a/src/Core/ChaCha20.php
+++ b/src/Core/ChaCha20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_ChaCha20', false)) {
     return;
diff --git a/src/Core/ChaCha20/Ctx.php b/src/Core/ChaCha20/Ctx.php
index 885b9ed5..a44b413b 100644
--- a/src/Core/ChaCha20/Ctx.php
+++ b/src/Core/ChaCha20/Ctx.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_ChaCha20_Ctx', false)) {
     return;
@@ -6,6 +7,9 @@
 
 /**
  * Class ParagonIE_Sodium_Core_ChaCha20_Ctx
+ *
+ * @template-implements ArrayAccess<int>
+ * @psalm-suppress MissingTemplateParam
  */
 class ParagonIE_Sodium_Core_ChaCha20_Ctx extends ParagonIE_Sodium_Core_Util implements ArrayAccess
 {
diff --git a/src/Core/ChaCha20/IetfCtx.php b/src/Core/ChaCha20/IetfCtx.php
index 3e5b9014..f75070a6 100644
--- a/src/Core/ChaCha20/IetfCtx.php
+++ b/src/Core/ChaCha20/IetfCtx.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_ChaCha20_IetfCtx', false)) {
     return;
diff --git a/src/Core/Curve25519.php b/src/Core/Curve25519.php
index b433fd8b..82c65ec5 100644
--- a/src/Core/Curve25519.php
+++ b/src/Core/Curve25519.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519', false)) {
     return;
diff --git a/src/Core/Curve25519/Fe.php b/src/Core/Curve25519/Fe.php
index ec579b83..75fc2243 100644
--- a/src/Core/Curve25519/Fe.php
+++ b/src/Core/Curve25519/Fe.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Fe', false)) {
     return;
@@ -8,6 +9,8 @@
  * Class ParagonIE_Sodium_Core_Curve25519_Fe
  *
  * This represents a Field Element
+ *
+ * @psalm-suppress MissingTemplateParam
  */
 class ParagonIE_Sodium_Core_Curve25519_Fe implements ArrayAccess
 {
@@ -98,6 +101,7 @@ public function offsetUnset($offset)
      *
      * @param int $offset
      * @return int
+     * @psalm-suppress ImplementedReturnTypeMismatch
      */
     #[ReturnTypeWillChange]
     public function offsetGet($offset)
diff --git a/src/Core/Curve25519/Ge/Cached.php b/src/Core/Curve25519/Ge/Cached.php
index 7966181e..a1888488 100644
--- a/src/Core/Curve25519/Ge/Cached.php
+++ b/src/Core/Curve25519/Ge/Cached.php
@@ -1,5 +1,5 @@
 <?php
-
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Ge_Cached', false)) {
     return;
diff --git a/src/Core/Curve25519/Ge/P1p1.php b/src/Core/Curve25519/Ge/P1p1.php
index 5168ac6c..02c25538 100644
--- a/src/Core/Curve25519/Ge/P1p1.php
+++ b/src/Core/Curve25519/Ge/P1p1.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Ge_P1p1', false)) {
     return;
diff --git a/src/Core/Curve25519/Ge/P2.php b/src/Core/Curve25519/Ge/P2.php
index be53cdb8..aa2a1c4f 100644
--- a/src/Core/Curve25519/Ge/P2.php
+++ b/src/Core/Curve25519/Ge/P2.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Ge_P2', false)) {
     return;
diff --git a/src/Core/Curve25519/Ge/P3.php b/src/Core/Curve25519/Ge/P3.php
index 1ff1ba73..2474bf31 100644
--- a/src/Core/Curve25519/Ge/P3.php
+++ b/src/Core/Curve25519/Ge/P3.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Ge_P3', false)) {
     return;
diff --git a/src/Core/Curve25519/Ge/Precomp.php b/src/Core/Curve25519/Ge/Precomp.php
index 3c8e5d61..1e9a5eb3 100644
--- a/src/Core/Curve25519/Ge/Precomp.php
+++ b/src/Core/Curve25519/Ge/Precomp.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_Ge_Precomp', false)) {
     return;
diff --git a/src/Core/Curve25519/H.php b/src/Core/Curve25519/H.php
index 50e60027..19def1dd 100644
--- a/src/Core/Curve25519/H.php
+++ b/src/Core/Curve25519/H.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Curve25519_H', false)) {
     return;
diff --git a/src/Core/Ed25519.php b/src/Core/Ed25519.php
index ee357515..fba4948d 100644
--- a/src/Core/Ed25519.php
+++ b/src/Core/Ed25519.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Ed25519', false)) {
     return;
diff --git a/src/Core/HChaCha20.php b/src/Core/HChaCha20.php
index 170c90b3..457d20c1 100644
--- a/src/Core/HChaCha20.php
+++ b/src/Core/HChaCha20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_HChaCha20', false)) {
     return;
diff --git a/src/Core/HSalsa20.php b/src/Core/HSalsa20.php
index b6f91a74..85e70308 100644
--- a/src/Core/HSalsa20.php
+++ b/src/Core/HSalsa20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_HSalsa20', false)) {
     return;
diff --git a/src/Core/Poly1305.php b/src/Core/Poly1305.php
index ca278be4..5f0767ef 100644
--- a/src/Core/Poly1305.php
+++ b/src/Core/Poly1305.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Poly1305', false)) {
     return;
diff --git a/src/Core/Poly1305/State.php b/src/Core/Poly1305/State.php
index 6c6717f2..15c1de3f 100644
--- a/src/Core/Poly1305/State.php
+++ b/src/Core/Poly1305/State.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Poly1305_State', false)) {
     return;
diff --git a/src/Core/Ristretto255.php b/src/Core/Ristretto255.php
index be1a06ca..8c0ac5c4 100644
--- a/src/Core/Ristretto255.php
+++ b/src/Core/Ristretto255.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 /**
  * Class ParagonIE_Sodium_Core_Ristretto255
diff --git a/src/Core/Salsa20.php b/src/Core/Salsa20.php
index a160bfe7..a1ddd920 100644
--- a/src/Core/Salsa20.php
+++ b/src/Core/Salsa20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Salsa20', false)) {
     return;
diff --git a/src/Core/SecretStream/State.php b/src/Core/SecretStream/State.php
index add0d450..5aa84e31 100644
--- a/src/Core/SecretStream/State.php
+++ b/src/Core/SecretStream/State.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 /**
  * Class ParagonIE_Sodium_Core_SecretStream_State
diff --git a/src/Core/SipHash.php b/src/Core/SipHash.php
index dfd3883d..ec869e3a 100644
--- a/src/Core/SipHash.php
+++ b/src/Core/SipHash.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_SipHash', false)) {
     return;
@@ -159,6 +160,8 @@ public static function rotl_64(int $int0, int $int1, int $c): array
      * @return string
      * @throws SodiumException
      * @throws TypeError
+     *
+     * @psalm-suppress PossiblyUndefinedArrayOffset
      */
     public static function sipHash24(
         #[SensitiveParameter]
diff --git a/src/Core/Util.php b/src/Core/Util.php
index d2129144..cc71d003 100644
--- a/src/Core/Util.php
+++ b/src/Core/Util.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_Util', false)) {
     return;
@@ -87,50 +88,6 @@ public static function bin2hex(
         return $hex;
     }
 
-    /**
-     * Convert a binary string into a hexadecimal string without cache-timing
-     * leaks, returning uppercase letters (as per RFC 4648)
-     *
-     * @internal You should not use this directly from another application
-     *
-     * @param string $bin_string (raw binary)
-     * @return string
-     * @throws TypeError
-     */
-    public static function bin2hexUpper(
-        #[SensitiveParameter]
-        string $bin_string
-    ): string {
-        $hex = '';
-        $len = self::strlen($bin_string);
-        for ($i = 0; $i < $len; ++$i) {
-            /** @var array<int, int> $chunk */
-            $chunk = unpack('C', $bin_string[$i]);
-            /**
-             * Lower 16 bits
-             */
-            $c = $chunk[1] & 0xf;
-
-            /**
-             * Upper 16 bits
-             */
-            $b = $chunk[1] >> 4;
-
-            /**
-             * Use pack() and binary operators to turn the two integers
-             * into hexadecimal characters. We don't use chr() here, because
-             * it uses a lookup table internally and we want to avoid
-             * cache-timing side-channels.
-             */
-            $hex .= pack(
-                'CC',
-                (55 + $b + ((($b - 10) >> 8) & ~6)),
-                (55 + $c + ((($c - 10) >> 8) & ~6))
-            );
-        }
-        return $hex;
-    }
-
     /**
      * Cache-timing-safe variant of ord()
      *
@@ -191,85 +148,6 @@ public static function compare(
         return ($gt + $gt + $eq) - 1;
     }
 
-    /**
-     * If a variable does not match a given type, throw a TypeError.
-     *
-     * @param mixed $mixedVar
-     * @param string $type
-     * @param int $argumentIndex
-     * @throws TypeError
-     * @throws SodiumException
-     * @return void
-     */
-    public static function declareScalarType(
-        #[SensitiveParameter]
-        mixed &$mixedVar = null,
-        string $type = 'void',
-        int $argumentIndex = 0
-    ): void {
-        if (func_num_args() === 0) {
-            /* Tautology, by default */
-            return;
-        }
-        if (func_num_args() === 1) {
-            throw new TypeError('Declared void, but passed a variable');
-        }
-        $realType = strtolower(gettype($mixedVar));
-        $type = strtolower($type);
-        switch ($type) {
-            case 'null':
-                if ($mixedVar !== null) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be null, ' . $realType . ' given.');
-                }
-                break;
-            case 'integer':
-            case 'int':
-                $allow = array('int', 'integer');
-                if (!in_array($type, $allow)) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be an integer, ' . $realType . ' given.');
-                }
-                $mixedVar = (int) $mixedVar;
-                break;
-            case 'boolean':
-            case 'bool':
-                $allow = array('bool', 'boolean');
-                if (!in_array($type, $allow)) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be a boolean, ' . $realType . ' given.');
-                }
-                $mixedVar = (bool) $mixedVar;
-                break;
-            case 'string':
-                if (!is_string($mixedVar)) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be a string, ' . $realType . ' given.');
-                }
-                break;
-            case 'decimal':
-            case 'double':
-            case 'float':
-                $allow = array('decimal', 'double', 'float');
-                if (!in_array($type, $allow)) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be a float, ' . $realType . ' given.');
-                }
-                $mixedVar = (float) $mixedVar;
-                break;
-            case 'object':
-                if (!is_object($mixedVar)) {
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be an object, ' . $realType . ' given.');
-                }
-                break;
-            case 'array':
-                if (!is_array($mixedVar)) {
-                    if ($mixedVar instanceof ArrayAccess) {
-                        return;
-                    }
-                    throw new TypeError('Argument ' . $argumentIndex . ' must be an array, ' . $realType . ' given.');
-                }
-                break;
-            default:
-                throw new SodiumException('Unknown type (' . $realType .') does not match expect type (' . $type . ')');
-        }
-    }
-
     /**
      * Evaluate whether or not two strings are equal (in constant-time)
      *
@@ -570,6 +448,7 @@ public static function mul(
      *
      * @param int|float $num
      * @return array<int, int>
+     * @psalm-suppress RedundantCastGivenDocblockType
      */
     public static function numericTo64BitInteger(int|float $num): array
     {
@@ -593,22 +472,7 @@ public static function numericTo64BitInteger(int|float $num): array
          * @var int $high
          * @var int $low
          */
-        return array($high, $low);
-    }
-
-    /**
-     * Store a 24-bit integer into a string, treating it as big-endian.
-     *
-     * @internal You should not use this directly from another application
-     *
-     * @param int $int
-     * @return string
-     * @throws TypeError
-     */
-    public static function store_3(int $int): string
-    {
-        $packed = pack('N', $int);
-        return self::substr($packed, 1, 3);
+        return array((int) $high, (int) $low);
     }
 
     /**
@@ -625,20 +489,6 @@ public static function store32_le(int $int): string
        return pack('V', $int);
     }
 
-    /**
-     * Store a 32-bit integer into a string, treating it as big-endian.
-     *
-     * @internal You should not use this directly from another application
-     *
-     * @param int $int
-     * @return string
-     * @throws TypeError
-     */
-    public static function store_4(int $int): string
-    {
-        return pack('N', $int);
-    }
-
     /**
      * Stores a 64-bit integer as an string, treating it as little-endian.
      *
diff --git a/src/Core/X25519.php b/src/Core/X25519.php
index 967d31fa..8090d43d 100644
--- a/src/Core/X25519.php
+++ b/src/Core/X25519.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_X25519', false)) {
     return;
diff --git a/src/Core/XChaCha20.php b/src/Core/XChaCha20.php
index e5b7a2e3..4e91dd79 100644
--- a/src/Core/XChaCha20.php
+++ b/src/Core/XChaCha20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_XChaCha20', false)) {
     return;
diff --git a/src/Core/XSalsa20.php b/src/Core/XSalsa20.php
index 7e77fb0e..ac183afb 100644
--- a/src/Core/XSalsa20.php
+++ b/src/Core/XSalsa20.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Core_XSalsa20', false)) {
     return;
diff --git a/src/Crypto.php b/src/Crypto.php
index 06114e11..bcd58c0d 100644
--- a/src/Crypto.php
+++ b/src/Crypto.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_Crypto', false)) {
     return;
@@ -743,6 +744,7 @@ public static function generichash(
         ParagonIE_Sodium_Core_BLAKE2b::pseudoConstructor();
 
         $k = null;
+        /** @psalm-suppress RiskyTruthyFalsyComparison */
         if (!empty($key)) {
             /** @var SplFixedArray $k */
             $k = ParagonIE_Sodium_Core_BLAKE2b::stringToSplFixedArray($key);
diff --git a/src/File.php b/src/File.php
index d9028142..239a8cc9 100644
--- a/src/File.php
+++ b/src/File.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('ParagonIE_Sodium_File', false)) {
     return;
diff --git a/src/SodiumException.php b/src/SodiumException.php
index 407e7287..b80c1590 100644
--- a/src/SodiumException.php
+++ b/src/SodiumException.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 if (class_exists('SodiumException', false)) {
     return;
diff --git a/tests/compat/FileCompatTest.php b/tests/compat/FileCompatTest.php
index b9b7f615..384f1a9b 100644
--- a/tests/compat/FileCompatTest.php
+++ b/tests/compat/FileCompatTest.php
@@ -38,5 +38,6 @@ public function testCompat()
 
         $this->assertTrue(ParagonIE_Sodium_File::verify($sigA, 'test.txt', $public));
         $this->assertTrue(sodium_crypto_sign_verify_detached($sigB, $message, $public));
+        unlink('test.txt');
     }
 }