--- /dev/null
+--- src/lib/sfdpgen/PriorityQueue.c.orig 2016-04-01 08:29:58.788223689 -0700
++++ src/lib/sfdpgen/PriorityQueue.c 2016-04-01 08:30:44.507731384 -0700
+@@ -11,6 +11,8 @@
+ * Contributors: See CVS logs. Details at http://www.graphviz.org/
+ *************************************************************************/
+
++void free(void *ptr);
++
+ #include "LinkedList.h"
+ #include "PriorityQueue.h"
+ #include "memory.h"