Index: addons/iio/CMakeLists.txt
===================================================================
--- addons/iio/CMakeLists.txt	(revision 10791)
+++ addons/iio/CMakeLists.txt	(working copy)
@@ -3,7 +3,7 @@
 
 include(FindPNG)
 if(PNG_FOUND)
-    set(ALLEGRO_CFG_IIO_HAVE_PNG 1)
+    set(ALLEGRO_CFG_IIO_HAVE_PNG "-DALLEGRO_CFG_IIO_HAVE_PNG")
     list(APPEND IIO_SOURCES png.c)
     set(IIO_LIBRARIES ${PNG_LIBRARIES})
     set(IIO_DEFINES ${PNG_DEFINITIONS})
@@ -20,7 +20,7 @@
         add_library(${target} ${libtype} ${IIO_SOURCES})
         set_target_properties(${target}
             PROPERTIES
-            COMPILE_FLAGS "${more_extra_flags} ${IIO_DEFINES} ${LIBRARY_CFLAGS} -DA5_IIO_SRC"
+            COMPILE_FLAGS "${more_extra_flags} ${IIO_DEFINES} ${LIBRARY_CFLAGS} -DA5_IIO_SRC ${ALLEGRO_CFG_IIO_HAVE_PNG}"
             OUTPUT_NAME ${nm2}
             )