diff --git a/crypto/mem.c b/crypto/mem.c
index b026fd38aa..0df0a2a549 100644
--- a/crypto/mem.c
+++ b/crypto/mem.c
@@ -175,6 +175,8 @@ void *CRYPTO_malloc_locked(int num, const char *file, int line)
 	void *ret = NULL;
 	extern unsigned char cleanse_ctr;
 
+	if (num < 0) return NULL;
+
 	allow_customize = 0;
 	if (malloc_debug_func != NULL)
 		{
@@ -214,6 +216,8 @@ void *CRYPTO_malloc(int num, const char *file, int line)
 	void *ret = NULL;
 	extern unsigned char cleanse_ctr;
 
+	if (num < 0) return NULL;
+
 	allow_customize = 0;
 	if (malloc_debug_func != NULL)
 		{
@@ -243,6 +247,8 @@ void *CRYPTO_realloc(void *str, int num, const char *file, int line)
 	if (str == NULL)
 		return CRYPTO_malloc(num, file, line);
 
+	if (num < 0) return NULL;
+
 	if (realloc_debug_func != NULL)
 		realloc_debug_func(str, NULL, num, file, line, 0);
 	ret = realloc_func(str,num);