--- backend/CMakeLists.txt.orig	2018-02-15 10:47:59 UTC
+++ backend/CMakeLists.txt
@@ -2,7 +2,8 @@
 
 project(zint)
 
-find_package(PNG)
+find_package(PNG REQUIRED)
+include_directories(${PNG_INCLUDE_DIR})
 
 set(zint_COMMON_SRCS common.c library.c render.c large.c reedsol.c gs1.c eci.c)
 set(zint_ONEDIM_SRCS code.c code128.c 2of5.c upcean.c telepen.c medical.c plessey.c rss.c)