https://bugs.gentoo.org/874447
--- a/plugins/png/qtpng.c
+++ b/plugins/png/qtpng.c
@@ -26,6 +26,7 @@
 #include <quicktime/colormodels.h>
 #include <png.h>
 #include <stdlib.h>
+#include <string.h>
 #include "qtpng.h"
 
 typedef struct