diff --git a/appveyor-build.cmd b/appveyor-build.cmd
index c6039fa11486..bd6a47095407 100644
--- a/appveyor-build.cmd
+++ b/appveyor-build.cmd
@@ -85,8 +85,8 @@ pushd tests
 call RunTests.cmd release fsharp Smoke
 @if ERRORLEVEL 1 type testresults\fsharp_failures.log && echo Error: 'RunTests.cmd release fsharp Smoke' failed && goto :failure
 
-call RunTests.cmd release fsharpqa Smoke
-@if ERRORLEVEL 1 type testresults\fsharpqa_failures.log && echo Error: 'RunTests.cmd release fsharpqa Smoke' failed && goto :failure
+call RunTests.cmd release fsharpqa Smoke CONFORMANCE06
+@if ERRORLEVEL 1 type testresults\fsharpqa_failures.log && echo Error: 'RunTests.cmd release fsharpqa Smoke CONFORMANCE06' failed && goto :failure
 
 call RunTests.cmd release compilerunit
 @if ERRORLEVEL 1 echo Error: 'RunTests.cmd release compilerunit' failed && goto :failure
diff --git a/src/fsharp/FSComp.txt b/src/fsharp/FSComp.txt
index 2f43466da65d..d338e664abcf 100644
--- a/src/fsharp/FSComp.txt
+++ b/src/fsharp/FSComp.txt
@@ -1139,6 +1139,7 @@ lexIndentOffForML,"Consider using a file with extension '.ml' or '.mli' instead"
 1242,parsMissingGreaterThan,"Unmatched '<'. Expected closing '>'"
 1243,parsUnexpectedQuotationOperatorInTypeAliasDidYouMeanVerbatimString,"Unexpected quotation operator '<@' in type definition. If you intend to pass a verbatim string as a static argument to a type provider, put a space between the '<' and '@' characters."
 1244,parsErrorParsingAsOperatorName,"Attempted to parse this as an operator name, but failed"
+1245,lexInvalidUnicodeLiteral,"This is not a valid UTF-16 literal"
 # Fsc.exe resource strings
 fscTooManyErrors,"Exiting - too many errors"
 2001,docfileNoXmlSuffix,"The documentation file has no .xml suffix"
diff --git a/src/fsharp/lex.fsl b/src/fsharp/lex.fsl
index 2c37ee00d934..a39b130b98ca 100644
--- a/src/fsharp/lex.fsl
+++ b/src/fsharp/lex.fsl
@@ -752,8 +752,12 @@ and string sargs skip = parse
       
  | unicodeGraphShort
     { let (buf,_fin,m,args) = sargs 
-      addUnicodeChar buf (int (unicodeGraphShort (lexemeTrimLeft lexbuf 2)));
-      if not skip then (STRING_TEXT (LexCont.String(!args.ifdefStack,m)))  else string sargs skip lexbuf  }
+      let c = int (unicodeGraphShort (lexemeTrimLeft lexbuf 2))
+      if c >= 0xD800 && c <= 0xD8FF then
+          fail args lexbuf (FSComp.SR.lexInvalidUnicodeLiteral()) (CHAR (char c))
+      else
+          addUnicodeChar buf c;
+          if not skip then (STRING_TEXT (LexCont.String(!args.ifdefStack,m)))  else string sargs skip lexbuf  }
      
  | unicodeGraphLong
     { let (buf,_fin,m,args) = sargs 
diff --git a/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/E_InvalidUnicodeChar01.fs b/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/E_InvalidUnicodeChar01.fs
new file mode 100644
index 000000000000..850578ec8645
--- /dev/null
+++ b/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/E_InvalidUnicodeChar01.fs
@@ -0,0 +1,18 @@
+// #Regression #Conformance #LexicalAnalysis 
+#light
+
+// Verify error when trying to take the byte value of 
+// a unicode character literal.
+
+//<Expects id="FS1245" span="(11,17-11,18)" status="error">This is not a valid UTF-16 literal</Expects>
+//<Expects id="FS1245" span="(13,17-11,18)" status="error">This is not a valid UTF-16 literal</Expects>
+
+let _ = '\uD7FF' // Ok
+
+let _ = '\uD800'
+
+let _ = "\uDFFF"
+
+let _ = "\uE000" // Ok
+
+exit 1
diff --git a/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/env.lst b/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/env.lst
index 2880802f9251..92cac21288ae 100644
--- a/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/env.lst
+++ b/tests/fsharpqa/Source/Conformance/LexicalAnalysis/StringsAndCharacters/env.lst
@@ -23,6 +23,7 @@
 
 	SOURCE=E_ByteStrUnicodeChar01.fs	# E_ByteStrUnicodeChar01.fs
 	SOURCE=E_ByteCharUnicodeChar01.fs	# E_ByteCharUnicodeChar01.fs
+	SOURCE=E_InvalidUnicodeChar01.fs	# E_InvalidUnicodeChar01.fs
 
 	SOURCE=E_MalformedShortUnicode01.fs  SCFLAGS="--test:ErrorRanges"	# E_MalformedShortUnicode01.fs
 	SOURCE=UnicodeString03.fs						# UnicodeString03.fs