diff --git a/org.lflang/src/org/lflang/AttributeUtils.java b/org.lflang/src/org/lflang/AttributeUtils.java
index 8e52048fea..ee8cef1bbf 100644
--- a/org.lflang/src/org/lflang/AttributeUtils.java
+++ b/org.lflang/src/org/lflang/AttributeUtils.java
@@ -42,6 +42,7 @@
 import org.lflang.lf.Reactor;
 import org.lflang.lf.StateVar;
 import org.lflang.lf.Timer;
+import org.lflang.util.StringUtil;
 
 /**
  * A helper class for processing attributes in the AST.
@@ -105,7 +106,7 @@ public static String getFirstArgumentValue(Attribute attr) {
         if (attr == null || attr.getAttrParms().isEmpty()) {
             return null;
         }
-        return attr.getAttrParms().get(0).getValue();
+        return StringUtil.removeQuotes(attr.getAttrParms().get(0).getValue());
     }
 
     /**
diff --git a/org.lflang/src/org/lflang/util/StringUtil.java b/org.lflang/src/org/lflang/util/StringUtil.java
index 3352796e12..9be21d46e8 100644
--- a/org.lflang/src/org/lflang/util/StringUtil.java
+++ b/org.lflang/src/org/lflang/util/StringUtil.java
@@ -73,13 +73,23 @@ public static String removeQuotes(String str) {
         if (str.length() < 2) {
             return str;
         }
-        if (str.startsWith("\"") && str.endsWith("\"")
-            || str.startsWith("'") && str.endsWith("'")) {
+        if (hasQuotes(str)) {
             return str.substring(1, str.length() - 1);
         }
         return str;
     }
 
+    /**
+     * Return true if the given string is surrounded by single or double
+     * quotes,
+     */
+    public static boolean hasQuotes(String str) {
+        if (str == null) {
+            return false;
+        }
+        return str.startsWith("\"") && str.endsWith("\"") || str.startsWith("'") && str.endsWith("'");
+    }
+
     /**
      * Intelligently trim the white space in a code block.
 	 *
diff --git a/org.lflang/src/org/lflang/validation/AttributeSpec.java b/org.lflang/src/org/lflang/validation/AttributeSpec.java
index dcd141870b..766621e595 100644
--- a/org.lflang/src/org/lflang/validation/AttributeSpec.java
+++ b/org.lflang/src/org/lflang/validation/AttributeSpec.java
@@ -36,6 +36,7 @@
 import org.lflang.lf.AttrParm;
 import org.lflang.lf.Attribute;
 import org.lflang.lf.LfPackage.Literals;
+import org.lflang.util.StringUtil;
 
 /**
  * Specification of the structure of an attribute annotation.
@@ -155,28 +156,35 @@ private boolean isOptional() {
         // Check if a parameter has the right type.
         // Currently only String, Int, Boolean, and Float are supported.
         public void check(LFValidator validator, AttrParm parm) {
-            switch(type) {
-                case STRING:
-                    // nothing to check, all literals are reported as strings
-                    break;
-                case INT:
-                    if (!ASTUtils.isInteger(parm.getValue())) {
-                        validator.error("Incorrect type: \"" + parm.getName() + "\"" + " should have type Int.",
-                                        Literals.ATTRIBUTE__ATTR_NAME);
-                    }
-                    break;
-                case BOOLEAN:
-                    if (!ASTUtils.isBoolean(parm.getValue())) {
-                        validator.error("Incorrect type: \"" + parm.getName() + "\"" + " should have type Boolean.",
-                                        Literals.ATTRIBUTE__ATTR_NAME);
-                    }
-                    break;
-                case FLOAT:
-                    if (!ASTUtils.isFloat(parm.getValue())) {
-                        validator.error("Incorrect type: \"" + parm.getName() + "\"" + " should have type Float.",
-                                        Literals.ATTRIBUTE__ATTR_NAME);
-                    }
-                    break;
+            switch (type) {
+            case STRING:
+                if (!StringUtil.hasQuotes(parm.getValue())) {
+                    validator.error("Incorrect type: \"" + parm.getName() + "\""
+                            + " should have type String.",
+                        Literals.ATTRIBUTE__ATTR_NAME);
+                }
+                break;
+            case INT:
+                if (!ASTUtils.isInteger(parm.getValue())) {
+                    validator.error(
+                        "Incorrect type: \"" + parm.getName() + "\"" + " should have type Int.",
+                        Literals.ATTRIBUTE__ATTR_NAME);
+                }
+                break;
+            case BOOLEAN:
+                if (!ASTUtils.isBoolean(parm.getValue())) {
+                    validator.error(
+                        "Incorrect type: \"" + parm.getName() + "\"" + " should have type Boolean.",
+                        Literals.ATTRIBUTE__ATTR_NAME);
+                }
+                break;
+            case FLOAT:
+                if (!ASTUtils.isFloat(parm.getValue())) {
+                    validator.error(
+                        "Incorrect type: \"" + parm.getName() + "\"" + " should have type Float.",
+                        Literals.ATTRIBUTE__ATTR_NAME);
+                }
+                break;
             }
         }
     }