diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index a16038f709893..fc66dbfcbe7a7 100644
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -469,7 +469,7 @@ if( MSVC )
   # though that we should handle it.  We do so by simply checking that
   # the DIA SDK folder exists.  Should this happen you will need to
   # uninstall VS 2012 and then re-install VS 2013.
-  if (IS_DIRECTORY ${MSVC_DIA_SDK_DIR})
+  if (IS_DIRECTORY "${MSVC_DIA_SDK_DIR}")
     set(HAVE_DIA_SDK 1)
   else()
     set(HAVE_DIA_SDK 0)