diff --git a/pjsip/build/Makefile b/pjsip/build/Makefile
index 4a7c9a2..6466c57 100644
--- a/pjsip/build/Makefile
+++ b/pjsip/build/Makefile
@@ -110,7 +110,7 @@
 
 doc:
 	cd .. && rm -rf docs/html docs/latex && doxygen docs/doxygen.cfg
-	@if test ! "$(WWWDIR)" == ""; then \
+	@if [ -n "$(WWWDIR)" ]; then \
 		echo "Copying to $(WWWDIR)/pjsip/docs/html.." ; \
 		cp -a ../docs/html/* $(WWWDIR)/pjsip/docs/html/ ; \
 	fi