diff --git a/src/Cassette.Aspnet.UnitTests/PlaceholderRewriter.cs b/src/Cassette.Aspnet.UnitTests/PlaceholderRewriter.cs
index 5a2482df..f2aeb84d 100644
--- a/src/Cassette.Aspnet.UnitTests/PlaceholderRewriter.cs
+++ b/src/Cassette.Aspnet.UnitTests/PlaceholderRewriter.cs
@@ -49,6 +49,18 @@ public void GivenCanRewriteOutput_WhenRewriteOutput_ThenPlaceholderReplacingResp
             response.VerifySet(r => r.Filter = It.IsAny<PlaceholderReplacingResponseFilter>());
         }
 
+        [Fact]
+        public void GivenWithCharsetCanRewriteOutput_WhenRewriteOutput_ThenPlaceholderReplacingResponseFilterSetForResponse()
+        {
+            settings.IsHtmlRewritingEnabled = true;
+            ContentType("text/html; charset=utf-8");
+            StatusCode(200);
+
+            rewriter.RewriteOutput();
+
+            response.VerifySet(r => r.Filter = It.IsAny<PlaceholderReplacingResponseFilter>());
+        }
+
         [Fact]
         public void GivenXhtmlContentType_WhenRewriteOutput_ThenPlaceholderReplacingResponseFilterSetForResponse()
         {
@@ -61,6 +73,18 @@ public void GivenXhtmlContentType_WhenRewriteOutput_ThenPlaceholderReplacingResp
             response.VerifySet(r => r.Filter = It.IsAny<PlaceholderReplacingResponseFilter>());
         }
 
+        [Fact]
+        public void GivenXhtmlContentTypeWithCharset_WhenRewriteOutput_ThenPlaceholderReplacingResponseFilterSetForResponse()
+        {
+            settings.IsHtmlRewritingEnabled = true;
+            ContentType("application/xhtml+xml; charset=utf-8");
+            StatusCode(200);
+
+            rewriter.RewriteOutput();
+
+            response.VerifySet(r => r.Filter = It.IsAny<PlaceholderReplacingResponseFilter>());
+        }
+
         [Fact]
         public void GivenStatusCodeIsRedirect_WhenRewriteOutput_ThenFilterNotInstalled()
         {
diff --git a/src/Cassette.Aspnet/PlaceholderRewriter.cs b/src/Cassette.Aspnet/PlaceholderRewriter.cs
index ce20cf0a..f640c1b8 100644
--- a/src/Cassette.Aspnet/PlaceholderRewriter.cs
+++ b/src/Cassette.Aspnet/PlaceholderRewriter.cs
@@ -58,8 +58,8 @@ bool CanRewriteOutput(HttpContextBase httpContext)
 
         bool IsHtmlResponse(HttpContextBase httpContext)
         {
-            return httpContext.Response.ContentType == "text/html" ||
-                   httpContext.Response.ContentType == "application/xhtml+xml";
+            return httpContext.Response.ContentType.StartsWith("text/html") ||
+                   httpContext.Response.ContentType.StartsWith("application/xhtml+xml");
         }
     }
 }
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