diff --git a/config.lib b/config.lib
--- a/config.lib
+++ b/config.lib
@@ -3543,7 +3543,8 @@ showhelp() {
 	echo "  --with-liblzma[=\"pkg-config liblzma\"]"
 	echo "                                 enables liblzma support"
 	echo "  --with-liblzo2[=liblzo2.a]     enables liblzo2 support"
-	echo "  --with-png[=libpng-config]     enables libpng support"
+	echo "  --with-png[=\"pkg-config libpng\"]"
+	echo "                                 enables libpng support"
 	echo "  --with-freetype[=\"pkg-config freetype2\"]"
 	echo "                                 enables libfreetype support"
 	echo "  --with-fontconfig[=\"pkg-config fontconfig\"]"