diff --git a/Makefile b/Makefile
index 2d4c021cb2..884db7c3b8 100644
--- a/Makefile
+++ b/Makefile
@@ -468,7 +468,7 @@ doc/core-en_US.xml: makeopts .lastclean $(XML_core_en_US)
 	@echo "<docs xmlns:xi=\"http://www.w3.org/2001/XInclude\">" >> $@
 	@for x in $(MOD_SUBDIRS); do \
 		printf "$$x " ; \
-		for i in `find $$x -name *.c`; do \
+		for i in `find $$x -name '*.c'`; do \
 			$(AWK) -f build_tools/get_documentation $$i >> $@ ; \
 		done ; \
 	done