diff --git a/Makefile b/Makefile
index 72e9c83733..4c68950e90 100644
--- a/Makefile
+++ b/Makefile
@@ -29,6 +29,7 @@ all check install installdirs installcheck installcheck-parallel uninstall clean
 	\
 	 if [ x"$${GMAKE+set}" = xset ]; then \
 	   echo "Using GNU make found at $${GMAKE}"; \
+	   unset MAKEFLAGS; unset MAKELEVEL; \
 	   $${GMAKE} $@ ; \
 	 else \
 	   echo "You must use GNU make to build PostgreSQL." ; \