--- a/make/hotspot/lib/JvmFlags.gmk	Mon Feb 11 11:01:00 2019 +0800
+++ b/make/hotspot/lib/JvmFlags.gmk	Mon Feb 11 12:12:41 2019 +0100
@@ -74,7 +74,7 @@
   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