diff --git a/build.cmd b/build.cmd
index 17cd00c39da..a017f925e8f 100644
--- a/build.cmd
+++ b/build.cmd
@@ -525,8 +525,8 @@ if '%BUILD_NET40%' == '1' (
     call src\update.cmd %BUILD_CONFIG% -ngen
 )
 
-@echo set NUNITPATH=packages\NUnit.ConsoleRunner.3.5.0\tools\
-set NUNITPATH=packages\NUnit.ConsoleRunner.3.5.0\tools\
+@echo set NUNITPATH=packages\NUnit.Console.3.0.0\tools\
+set NUNITPATH=packages\NUnit.Console.3.0.0\tools\
 if not exist %NUNITPATH% echo Error: Could not find %NUNITPATH% && goto :failure
 
 @echo xcopy "%NUNITPATH%*.*"  "%~dp0tests\fsharpqa\testenv\bin\nunit\*.*" /S /Q /Y
@@ -596,7 +596,7 @@ setlocal enableDelayedExpansion
 
 
 set NUNITPATH=%~dp0tests\fsharpqa\testenv\bin\nunit\
-set NUNIT3_CONSOLE=%~dp0packages\NUnit.ConsoleRunner.3.5.0\tools\nunit3-console.exe
+set NUNIT3_CONSOLE=%~dp0packages\NUnit.Console.3.0.0\tools\nunit3-console.exe
 set link_exe=%~dp0packages\VisualCppTools.14.0.24519-Pre\lib\native\bin\link.exe
 if not exist "%link_exe%" (
     echo Error: failed to find '%link_exe%' use nuget to restore the VisualCppTools package
diff --git a/packages.config b/packages.config
index dd84372923b..6e0a76090e8 100644
--- a/packages.config
+++ b/packages.config
@@ -21,7 +21,7 @@
   <!-- Testing -->
   <package id="FsCheck" version="2.0.3" />
   <package id="NUnit" version="3.5.0" targetFramework="net45" />
-  <package id="NUnit.ConsoleRunner" version="3.5.0" targetFramework="net45" />
+  <package id="NUnit.Console" version="3.0.0" targetFramework="net45" />
   <package id="NUnitLite" version="3.5.0" targetFramework="net45" />
   <package id="NUnit3TestAdapter" version="3.0.8-ctp-8" targetFramework="net45" />
   <package id="BenchmarkDotNet" version="0.9.8"/>
diff --git a/src/utils/filename.fs b/src/utils/filename.fs
index ad494a0fd75..e80a4564998 100644
--- a/src/utils/filename.fs
+++ b/src/utils/filename.fs
@@ -29,16 +29,18 @@ let checkPathForIllegalChars (path:string) =
 // Case sensitive (original behaviour preserved).
 let checkSuffix (x:string) (y:string) = x.EndsWith(y,System.StringComparison.Ordinal) 
 
-let hasExtension (s:string) = 
-    checkPathForIllegalChars s
+let hasExtensionWithValidate (validate:bool) (s:string) = 
+    if validate then  (checkPathForIllegalChars s) |> ignore
     let sLen = s.Length
     (sLen >= 1 && s.[sLen - 1] = '.' && s <> ".." && s <> ".") 
     || Path.HasExtension(s)
 
+let hasExtension (s:string) = hasExtensionWithValidate true s
+
 let chopExtension (s:string) =
     checkPathForIllegalChars s
     if s = "." then "" else // for OCaml compatibility
-    if not (hasExtension s) then 
+    if not (hasExtensionWithValidate false s) then 
         raise (System.ArgumentException("chopExtension")) // message has to be precisely this, for OCaml compatibility, and no argument name can be set
     Path.Combine (Path.GetDirectoryName s,Path.GetFileNameWithoutExtension(s))