diff --git a/src/Compilers/CSharp/Portable/Parser/Blender.Reader.cs b/src/Compilers/CSharp/Portable/Parser/Blender.Reader.cs
index 86d28a378a1c3..2473f565d7510 100644
--- a/src/Compilers/CSharp/Portable/Parser/Blender.Reader.cs
+++ b/src/Compilers/CSharp/Portable/Parser/Blender.Reader.cs
@@ -305,6 +305,7 @@ private static bool IsFabricatedToken(SyntaxKind kind)
                 {
                     case SyntaxKind.GreaterThanGreaterThanToken:
                     case SyntaxKind.GreaterThanGreaterThanEqualsToken:
+                    case SyntaxKind.ExclamationExclamationToken:
                         return true;
                     default:
                         return SyntaxFacts.IsContextualKeyword(kind);
diff --git a/src/Compilers/CSharp/Test/Syntax/IncrementalParsing/IncrementalParsingTests.cs b/src/Compilers/CSharp/Test/Syntax/IncrementalParsing/IncrementalParsingTests.cs
index e6d26e31e0e5f..55ca1cf5ea734 100644
--- a/src/Compilers/CSharp/Test/Syntax/IncrementalParsing/IncrementalParsingTests.cs
+++ b/src/Compilers/CSharp/Test/Syntax/IncrementalParsing/IncrementalParsingTests.cs
@@ -28,13 +28,19 @@ private SyntaxTree Parse(string text, params string[] defines)
             return SyntaxFactory.ParseSyntaxTree(itext, options);
         }
 
-        private SyntaxTree Parse6(string text)
+        private SyntaxTree Parse(string text, LanguageVersion languageVersion)
         {
-            var options = new CSharpParseOptions(languageVersion: LanguageVersion.CSharp6);
+            var options = new CSharpParseOptions(languageVersion: languageVersion);
             var itext = SourceText.From(text);
             return SyntaxFactory.ParseSyntaxTree(itext, options);
         }
 
+        private SyntaxTree Parse6(string text)
+            => Parse(text, LanguageVersion.CSharp6);
+
+        private SyntaxTree ParsePreview(string text)
+            => Parse(text, LanguageVersion.Preview);
+
         [Fact]
         public void TestChangeClassNameWithNonMatchingMethod()
         {
@@ -51,6 +57,31 @@ public void TestChangeClassNameWithNonMatchingMethod()
                             SyntaxKind.IdentifierToken);
         }
 
+        [Fact]
+        public void TestExclamationExclamation()
+        {
+            var text = @"#nullable enable
+
+public class C {
+    public void M(string? x  !!) { // no error.
+    }
+}";
+            var oldTree = this.ParsePreview(text);
+            var newTree = oldTree.WithReplaceFirst("?", "");
+            Assert.Equal(0, oldTree.GetCompilationUnitRoot().Errors().Length);
+            Assert.Equal(0, newTree.GetCompilationUnitRoot().Errors().Length);
+
+            var diffs = SyntaxDifferences.GetRebuiltNodes(oldTree, newTree);
+            TestDiffsInOrder(diffs,
+                            SyntaxKind.CompilationUnit,
+                            SyntaxKind.ClassDeclaration,
+                            SyntaxKind.MethodDeclaration,
+                            SyntaxKind.ParameterList,
+                            SyntaxKind.Parameter,
+                            SyntaxKind.PredefinedType,
+                            SyntaxKind.StringKeyword);
+        }
+
         [Fact]
         public void TestChangeClassNameToNotMatchConstructor()
         {