Index: main/astmm.c
===================================================================
--- main/astmm.c	(revision 143349)
+++ main/astmm.c	(working copy)
@@ -156,10 +156,15 @@
 
 static void __ast_free_region(void *ptr, const char *file, int lineno, const char *func)
 {
-	int hash = HASH(ptr);
+	int hash;
 	struct ast_region *reg, *prev = NULL;
 	unsigned int *fence;
 
+	if (!ptr)
+		return;
+
+	hash = HASH(ptr);
+
 	ast_mutex_lock(&reglock);
 	for (reg = regions[hash]; reg; reg = reg->next) {
 		if (reg->data == ptr) {