diff --git a/scripts/AddGTest.cmake b/scripts/AddGTest.cmake
index 4b5e36f..a8f7c52 100644
--- a/scripts/AddGTest.cmake
+++ b/scripts/AddGTest.cmake
@@ -19,11 +19,13 @@ macro(add_gtest name source)
     #                       "${source_dir}/include;${THISTEST_INCLUDE}")
 
     add_executable(test_${name} ${source})
-    if(MSVC)
+    if(EXISTS ${EXTERNAL_ROOT}/lib/gtest.lib)
       target_link_libraries(test_${name} ${EXTERNAL_ROOT}/lib/gtest.lib)
-    else(MSVC)
+    elseif(EXISTS ${EXTERNAL_ROOT}/lib/libgtest.a)
       target_link_libraries(test_${name} ${EXTERNAL_ROOT}/lib/libgtest.a)
-    endif(MSVC)
+    elseif(NOT GTest_LOOKUP_BUILD)
+      message(FATAL_ERROR "Could not find gtest")
+    endif()
     if(CMAKE_THREAD_LIBS_INIT)
       target_link_libraries(test_${name} ${CMAKE_THREAD_LIBS_INIT})
     endif(CMAKE_THREAD_LIBS_INIT)