diff --git a/src/test/OpenEXRCoreTest/compressionTables.cpp b/src/test/OpenEXRCoreTest/compressionTables.cpp
index 5cd5b0ec5..950fa09ec 100644
--- a/src/test/OpenEXRCoreTest/compressionTables.cpp
+++ b/src/test/OpenEXRCoreTest/compressionTables.cpp
@@ -519,7 +519,7 @@ testDWATable (const std::string&)
 #endif
 
 #ifndef USE_CLZ
-#    ifdef _WIN32
+#    ifdef _MSC_VER
 static int __inline __builtin_clz(uint32_t v)
 {
 #ifdef __BMI1__