diff --git a/libs/image/Makefile.am b/libs/image/Makefile.am
index 3998394da..4625e6996 100644
--- a/libs/image/Makefile.am
+++ b/libs/image/Makefile.am
@@ -1,6 +1,6 @@
 AUTOMAKE_OPTIONS= foreign
-AM_CFLAGS= @PREFER_PIC@
-INCLUDES= -I$(top_srcdir)/include
+AM_CFLAGS= @PREFER_PIC@ $(PNG_CFLAGS)
+AM_CPPFLAGS= -I$(top_srcdir)/include
 
 lib_LTLIBRARIES= libQFimage.la