diff --git a/CMakeLists.txt b/CMakeLists.txt
index 552cf77e8a6..69812be1e50 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -291,8 +291,9 @@ if(APPLE)
 			message(STATUS "Setting compiler to: " ${CMAKE_XCODE_ATTRIBUTE_GCC_VERSION})
 		endif()
 	else() # unix makefile generator does not fill XCODE_VERSION var, so we get it with a command
-		execute_process(COMMAND xcodebuild -version OUTPUT_VARIABLE XCODE_VERS_BUILDNR )
-		STRING(SUBSTRING ${XCODE_VERS_BUILDNR} 6 3 XCODE_VERSION) # truncate away build-nr
+		execute_process(COMMAND xcodebuild -version OUTPUT_VARIABLE XCODE_VERS_BUILD_NR)
+		string(SUBSTRING "${XCODE_VERS_BUILD_NR}" 6 3 XCODE_VERSION) # truncate away build-nr
+		unset(XCODE_VERS_BUILD_NR)
 	endif()
 	
 	message(STATUS "Detected Xcode-version: " ${XCODE_VERSION})