diff --git a/make/hotspot/lib/JvmFlags.gmk b/make/hotspot/lib/JvmFlags.gmk
index 251c731ea71..ced208167e0 100644
--- a/make/hotspot/lib/JvmFlags.gmk
+++ b/make/hotspot/lib/JvmFlags.gmk
@@ -74,7 +74,7 @@ ifeq ($(DEBUG_LEVEL), release)
   endif
 else ifeq ($(DEBUG_LEVEL), fastdebug)
   JVM_CFLAGS_DEBUGLEVEL := -DASSERT
-  ifeq ($call isTargetOs, windows aix), false)
+  ifeq ($(call isTargetOs, windows aix), false)
     # NOTE: Old build did not define CHECK_UNHANDLED_OOPS on Windows and AIX.
     JVM_CFLAGS_DEBUGLEVEL += -DCHECK_UNHANDLED_OOPS
   endif