diff --git a/src/formats.c b/src/formats.c
index d55377c..b90b43f 100644
--- a/src/formats.c
+++ b/src/formats.c
@@ -13,6 +13,7 @@
 #ifndef BENCH_BUILD
 #include "options.h"
 #endif
+#include "memory.h"
 
 struct fmt_main *fmt_list = NULL;
 static struct fmt_main **fmt_tail = &fmt_list;
@@ -61,6 +62,7 @@ char *fmt_self_test(struct fmt_main *format)
 	char *ciphertext, *plaintext;
 	int ntests, done, index, max, size;
 	void *binary, *salt;
+	char *null;
 
 	if (format->params.plaintext_length > PLAINTEXT_BUFFER_SIZE - 3)
 		return "length";
@@ -76,6 +78,9 @@ char *fmt_self_test(struct fmt_main *format)
 	current = format->params.tests;
 	if (ntests==0) return NULL;
 
+	null = mem_calloc_tiny(format->params.plaintext_length + 1,
+	                       MEM_ALIGN_WORD);
+
 	done = 0;
 	index = 0; max = format->params.max_keys_per_crypt;
 	do {
@@ -128,7 +133,7 @@ char *fmt_self_test(struct fmt_main *format)
 
 /* Remove some old keys to better test cmp_all() */
 		if (index & 1)
-			format->methods.set_key("", index);
+			format->methods.set_key(null, index);
 
 /* 0 1 2 3 4 6 9 13 19 28 42 63 94 141 211 316 474 711 1066 ... */
 		if (index >= 2 && max > ntests)