diff -Nur aMule-2.3.1-orig/m4/libpng.m4 aMule-2.3.1/m4/libpng.m4
--- aMule-2.3.1-orig/m4/libpng.m4	2011-10-08 21:05:07.000000000 +0200
+++ aMule-2.3.1/m4/libpng.m4	2012-02-05 14:08:00.000000000 +0100
@@ -95,9 +95,9 @@
 			SAVED_LDFLAGS=$LDFLAGS
 			SAVED_LIBS=$LIBS
 
-			CFLAGS+=" $LIBPNG_CFLAGS"
-			LDFLAGS+=" $LIBPNG_LDFLAGS"
-			LIBS+=" $LIBPNG_LIBS"
+			CFLAGS="$CFLAGS $LIBPNG_CFLAGS"
+			LDFLAGS="$LDFLAGS $LIBPNG_LDFLAGS"
+			LIBS="$LIBS $LIBPNG_LIBS"
 
 			AC_LINK_IFELSE([
 				AC_LANG_PROGRAM([[