diff --git a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsHttpServletResponse.java b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsHttpServletResponse.java
index 63a2dca80..3f0c1678e 100644
--- a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsHttpServletResponse.java
+++ b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsHttpServletResponse.java
@@ -435,11 +435,15 @@ public void flushBuffer() throws IOException {
         // The content type is json but we have no encoding specified, according to the RFC (https://tools.ietf.org/html/rfc4627#section-3)
         // we should attempt to detect the encoding. However, since we are running in Lambda we shouldn't even consider
         // big endian systems and it's highly unlikely we'll have apps using UTF-16/32 we simply force UTF-8
-        if (headers != null && headers.getFirst(HttpHeaders.CONTENT_TYPE) != null &&
-                headers.getFirst(HttpHeaders.CONTENT_TYPE).toLowerCase(Locale.getDefault()).trim().equals(MediaType.APPLICATION_JSON) &&
-                charset == null) {
-            charset = "UTF-8";
+        if (charset == null && headers != null && headers.getFirst(HttpHeaders.CONTENT_TYPE) != null) {
+            String contentTypeLower = headers.getFirst(HttpHeaders.CONTENT_TYPE).toLowerCase(Locale.ENGLISH).trim();
+            if (contentTypeLower.contains("charset=utf-8")) {
+                charset = "UTF-8";
+            } else if (contentTypeLower.equals(MediaType.APPLICATION_JSON)) {
+                charset = "UTF-8";
+            }
         }
+                
 
         // if at this point we are still null, we set the default
         if (charset == null) {
diff --git a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsServletContext.java b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsServletContext.java
index 6b027e37e..cc06f5ad9 100644
--- a/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsServletContext.java
+++ b/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsServletContext.java
@@ -136,11 +136,11 @@ public String getMimeType(String s) {
         if (mimeTypes == null) {
             mimeTypes = new MimetypesFileTypeMap();
         }
-        if (s.endsWith(".js")) {
-                return "application/javascript";
-        }
         if (s.endsWith(".css")) {
-                return "text/css";
+                return "text/css; charset=utf-8";
+        }
+        if (s.endsWith(".js")) {
+                return "application/javascript; charset=utf-8";
         }
         // TODO: The getContentType method of the MimetypesFileTypeMap returns application/octet-stream
         // instead of null when the type cannot be found. We should replace with an implementation that