diff --git a/src/Microsoft.AspNet.Razor/CodeGenerators/CSharpTagHelperCodeRenderer.cs b/src/Microsoft.AspNet.Razor/CodeGenerators/CSharpTagHelperCodeRenderer.cs
index 4bf8acaedb..8ecaefdedf 100644
--- a/src/Microsoft.AspNet.Razor/CodeGenerators/CSharpTagHelperCodeRenderer.cs
+++ b/src/Microsoft.AspNet.Razor/CodeGenerators/CSharpTagHelperCodeRenderer.cs
@@ -229,15 +229,10 @@ namespace Microsoft.AspNet.Razor.CodeGenerators
                     descriptor.Attributes.Any(attributeDescriptor => attributeDescriptor.IsNameMatch(attributeName)));
 
 
-                // Bound attributes have associated descriptors.
-                if (associatedDescriptors.Any())
+                // Bound attributes have associated descriptors. First attribute value wins if there are duplicates;
+                // later values of duplicate bound attributes are treated as if they were unbound.
+                if (associatedDescriptors.Any() && renderedBoundAttributeNames.Add(attributeName))
                 {
-                    if (!renderedBoundAttributeNames.Add(attributeName))
-                    {
-                        // First attribute value wins if there are duplicates.
-                        continue;
-                    }
-
                     if (attributeValueChunk == null)
                     {
                         // Minimized attributes are not valid for bound attributes. TagHelperBlockRewriter has already
diff --git a/test/Microsoft.AspNet.Razor.Test/CodeGenerators/CSharpTagHelperRenderingTest.cs b/test/Microsoft.AspNet.Razor.Test/CodeGenerators/CSharpTagHelperRenderingTest.cs
index c8c34f91fd..0ee768f192 100644
--- a/test/Microsoft.AspNet.Razor.Test/CodeGenerators/CSharpTagHelperRenderingTest.cs
+++ b/test/Microsoft.AspNet.Razor.Test/CodeGenerators/CSharpTagHelperRenderingTest.cs
@@ -879,6 +879,36 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                                 contentLength: 2),
                         }
                     },
+                    {
+                        "DuplicateAttributeTagHelpers",
+                        "DuplicateAttributeTagHelpers.DesignTime",
+                        DefaultPAndInputTagHelperDescriptors,
+                        new List<LineMapping>
+                        {
+                            BuildLineMapping(
+                                documentAbsoluteIndex: 14,
+                                documentLineIndex: 0,
+                                generatedAbsoluteIndex: 501,
+                                generatedLineIndex: 15,
+                                characterOffsetIndex: 14,
+                                contentLength: 17),
+                            BuildLineMapping(
+                                documentAbsoluteIndex: 146,
+                                documentLineIndex: 4,
+                                generatedAbsoluteIndex: 1567,
+                                generatedLineIndex: 43,
+                                characterOffsetIndex: 34,
+                                contentLength: 4),
+                            BuildLineMapping(
+                                documentAbsoluteIndex: 43,
+                                documentLineIndex: 2,
+                                documentCharacterOffsetIndex: 8,
+                                generatedAbsoluteIndex: 1730,
+                                generatedLineIndex: 49,
+                                generatedCharacterOffsetIndex: 19,
+                                contentLength: 1),
+                        }
+                    },
                 };
             }
         }
@@ -921,6 +951,7 @@ namespace Microsoft.AspNet.Razor.Test.Generator
                         "PrefixedAttributeTagHelpers.Reversed",
                         PrefixedAttributeTagHelperDescriptors.Reverse()
                     },
+                    { "DuplicateAttributeTagHelpers", null, DefaultPAndInputTagHelperDescriptors },
                 };
             }
         }
diff --git a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.DesignTime.cs b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.DesignTime.cs
new file mode 100644
index 0000000000..cec5d58b62
--- /dev/null
+++ b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.DesignTime.cs
@@ -0,0 +1,57 @@
+namespace TestOutput
+{
+    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+    using System;
+    using System.Threading.Tasks;
+
+    public class DuplicateAttributeTagHelpers
+    {
+        private static object @__o;
+        private void @__RazorDesignTimeHelpers__()
+        {
+            #pragma warning disable 219
+            string __tagHelperDirectiveSyntaxHelper = null;
+            __tagHelperDirectiveSyntaxHelper = 
+#line 1 "DuplicateAttributeTagHelpers.cshtml"
+              "something, nice"
+
+#line default
+#line hidden
+            ;
+            #pragma warning restore 219
+        }
+        #line hidden
+        private PTagHelper __PTagHelper = null;
+        private InputTagHelper __InputTagHelper = null;
+        private InputTagHelper2 __InputTagHelper2 = null;
+        #line hidden
+        public DuplicateAttributeTagHelpers()
+        {
+        }
+
+        #pragma warning disable 1998
+        public override async Task ExecuteAsync()
+        {
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+            __InputTagHelper.Type = "button";
+            __InputTagHelper2.Type = __InputTagHelper.Type;
+            __InputTagHelper = CreateTagHelper<InputTagHelper>();
+            __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+            __InputTagHelper.Type = "button";
+            __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 5 "DuplicateAttributeTagHelpers.cshtml"
+      __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+#line 3 "DuplicateAttributeTagHelpers.cshtml"
+__PTagHelper.Age = 3;
+
+#line default
+#line hidden
+        }
+        #pragma warning restore 1998
+    }
+}
diff --git a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.cs b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.cs
new file mode 100644
index 0000000000..833b1bffd0
--- /dev/null
+++ b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/DuplicateAttributeTagHelpers.cs
@@ -0,0 +1,101 @@
+#pragma checksum "DuplicateAttributeTagHelpers.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "af64a6adaf73e4143024a1145e70cbd3a24d2c0e"
+namespace TestOutput
+{
+    using Microsoft.AspNet.Razor.Runtime.TagHelpers;
+    using System;
+    using System.Threading.Tasks;
+
+    public class DuplicateAttributeTagHelpers
+    {
+        #line hidden
+        #pragma warning disable 0414
+        private TagHelperContent __tagHelperStringValueBuffer = null;
+        #pragma warning restore 0414
+        private TagHelperExecutionContext __tagHelperExecutionContext = null;
+        private TagHelperRunner __tagHelperRunner = null;
+        private TagHelperScopeManager __tagHelperScopeManager = new TagHelperScopeManager();
+        private PTagHelper __PTagHelper = null;
+        private InputTagHelper __InputTagHelper = null;
+        private InputTagHelper2 __InputTagHelper2 = null;
+        #line hidden
+        public DuplicateAttributeTagHelpers()
+        {
+        }
+
+        #pragma warning disable 1998
+        public override async Task ExecuteAsync()
+        {
+            __tagHelperRunner = __tagHelperRunner ?? new TagHelperRunner();
+            Instrumentation.BeginContext(33, 2, true);
+            WriteLiteral("\r\n");
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.Begin("p", false, "test", async() => {
+                Instrumentation.BeginContext(65, 6, true);
+                WriteLiteral("\r\n    ");
+                Instrumentation.EndContext();
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", true, "test", async() => {
+                }
+                , StartTagHelperWritingScope, EndTagHelperWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper.Type = "button";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+                __tagHelperExecutionContext.AddHtmlAttribute("TYPE", Html.Raw("checkbox"));
+                __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+                Instrumentation.BeginContext(71, 39, false);
+                await WriteTagHelperAsync(__tagHelperExecutionContext);
+                Instrumentation.EndContext();
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                Instrumentation.BeginContext(110, 6, true);
+                WriteLiteral("\r\n    ");
+                Instrumentation.EndContext();
+                __tagHelperExecutionContext = __tagHelperScopeManager.Begin("input", true, "test", async() => {
+                }
+                , StartTagHelperWritingScope, EndTagHelperWritingScope);
+                __InputTagHelper = CreateTagHelper<InputTagHelper>();
+                __tagHelperExecutionContext.Add(__InputTagHelper);
+                __InputTagHelper2 = CreateTagHelper<InputTagHelper2>();
+                __tagHelperExecutionContext.Add(__InputTagHelper2);
+                __InputTagHelper.Type = "button";
+                __tagHelperExecutionContext.AddTagHelperAttribute("type", __InputTagHelper.Type);
+                __InputTagHelper2.Type = __InputTagHelper.Type;
+#line 5 "DuplicateAttributeTagHelpers.cshtml"
+      __InputTagHelper2.Checked = true;
+
+#line default
+#line hidden
+                __tagHelperExecutionContext.AddTagHelperAttribute("checked", __InputTagHelper2.Checked);
+                __tagHelperExecutionContext.AddHtmlAttribute("type", Html.Raw("checkbox"));
+                __tagHelperExecutionContext.AddHtmlAttribute("checked", Html.Raw("false"));
+                __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+                Instrumentation.BeginContext(116, 70, false);
+                await WriteTagHelperAsync(__tagHelperExecutionContext);
+                Instrumentation.EndContext();
+                __tagHelperExecutionContext = __tagHelperScopeManager.End();
+                Instrumentation.BeginContext(186, 2, true);
+                WriteLiteral("\r\n");
+                Instrumentation.EndContext();
+            }
+            , StartTagHelperWritingScope, EndTagHelperWritingScope);
+            __PTagHelper = CreateTagHelper<PTagHelper>();
+            __tagHelperExecutionContext.Add(__PTagHelper);
+#line 3 "DuplicateAttributeTagHelpers.cshtml"
+__PTagHelper.Age = 3;
+
+#line default
+#line hidden
+            __tagHelperExecutionContext.AddTagHelperAttribute("age", __PTagHelper.Age);
+            __tagHelperExecutionContext.AddHtmlAttribute("AGE", Html.Raw("40"));
+            __tagHelperExecutionContext.AddHtmlAttribute("Age", Html.Raw("500"));
+            __tagHelperExecutionContext.Output = await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+            Instrumentation.BeginContext(35, 157, false);
+            await WriteTagHelperAsync(__tagHelperExecutionContext);
+            Instrumentation.EndContext();
+            __tagHelperExecutionContext = __tagHelperScopeManager.End();
+        }
+        #pragma warning restore 1998
+    }
+}
diff --git a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.Reversed.cs b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.Reversed.cs
index f577815d69..501f490065 100644
--- a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.Reversed.cs
+++ b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.Reversed.cs
@@ -166,6 +166,7 @@ __InputTagHelper2.IntDictionaryProperty["grabber"] = 42;
 #line hidden
             __tagHelperExecutionContext.AddTagHelperAttribute("int-prefix-pepper", __InputTagHelper2.IntDictionaryProperty["pepper"]);
             __InputTagHelper1.IntDictionaryProperty["pepper"] = __InputTagHelper2.IntDictionaryProperty["pepper"];
+            __tagHelperExecutionContext.AddHtmlAttribute("int-prefix-salt", Html.Raw("8"));
             __InputTagHelper2.StringDictionaryProperty["grabber"] = "string";
             __tagHelperExecutionContext.AddTagHelperAttribute("string-prefix-grabber", __InputTagHelper2.StringDictionaryProperty["grabber"]);
             __InputTagHelper1.StringProperty = __InputTagHelper2.StringDictionaryProperty["grabber"];
diff --git a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.cs b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.cs
index f0c9090e9a..9e22db40da 100644
--- a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.cs
+++ b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Output/PrefixedAttributeTagHelpers.cs
@@ -166,6 +166,7 @@ __InputTagHelper1.IntProperty = 42;
 #line hidden
             __tagHelperExecutionContext.AddTagHelperAttribute("int-prefix-pepper", __InputTagHelper1.IntDictionaryProperty["pepper"]);
             __InputTagHelper2.IntDictionaryProperty["pepper"] = __InputTagHelper1.IntDictionaryProperty["pepper"];
+            __tagHelperExecutionContext.AddHtmlAttribute("int-prefix-salt", Html.Raw("8"));
             __InputTagHelper1.StringProperty = "string";
             __tagHelperExecutionContext.AddTagHelperAttribute("string-prefix-grabber", __InputTagHelper1.StringProperty);
             __InputTagHelper2.StringDictionaryProperty["grabber"] = __InputTagHelper1.StringProperty;
diff --git a/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Source/DuplicateAttributeTagHelpers.cshtml b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Source/DuplicateAttributeTagHelpers.cshtml
new file mode 100644
index 0000000000..900a174557
--- /dev/null
+++ b/test/Microsoft.AspNet.Razor.Test/TestFiles/CodeGenerator/Source/DuplicateAttributeTagHelpers.cshtml
@@ -0,0 +1,6 @@
+@addTagHelper "something, nice"
+
+<p age="3" AGE="40" Age="500">
+    <input type="button" TYPE="checkbox" />
+    <input type="button" checked="true" type="checkbox" checked="false" />
+</p>
\ No newline at end of file