diff --git a/src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionUtils.cs b/src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionUtils.cs
index 525dc33ae6..1e917b595f 100644
--- a/src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionUtils.cs
+++ b/src/Microsoft.AspNetCore.ResponseCompression/ResponseCompressionUtils.cs
@@ -23,7 +23,7 @@ namespace Microsoft.AspNetCore.ResponseCompression
                 throw new ArgumentNullException(nameof(mimeTypes));
             }
 
-            var mimeTypeSet = new HashSet<string>(mimeTypes);
+            var mimeTypeSet = new HashSet<string>(mimeTypes, StringComparer.OrdinalIgnoreCase);
 
             return (httpContext) =>
             {
diff --git a/test/Microsoft.AspNetCore.ResponseCompression.Tests/ResponseCompressionUtilsTest.cs b/test/Microsoft.AspNetCore.ResponseCompression.Tests/ResponseCompressionUtilsTest.cs
index aae7752479..73fd2caea3 100644
--- a/test/Microsoft.AspNetCore.ResponseCompression.Tests/ResponseCompressionUtilsTest.cs
+++ b/test/Microsoft.AspNetCore.ResponseCompression.Tests/ResponseCompressionUtilsTest.cs
@@ -36,6 +36,7 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
 
         [Theory]
         [InlineData("text/plain")]
+        [InlineData("text/PLAIN")]
         [InlineData("text/plain; charset=ISO-8859-4")]
         [InlineData("text/plain ; charset=ISO-8859-4")]
         public void CreateShouldCompressResponseDelegate_WithCharset_Compress(string contentType)
@@ -53,7 +54,6 @@ namespace Microsoft.AspNetCore.ResponseCompression.Tests
         [Theory]
         [InlineData("")]
         [InlineData("text/plain2")]
-        [InlineData("text/PLAIN")]
         public void CreateShouldCompressResponseDelegate_OtherContentTypes_NoMatch(string contentType)
         {
             var httpContext = new DefaultHttpContext();