diff --git a/crypto/mem.c b/crypto/mem.c
index d7d3cda5d..29df7d35b 100644
--- a/crypto/mem.c
+++ b/crypto/mem.c
@@ -252,6 +252,8 @@ 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)
 		{
@@ -291,6 +293,8 @@ 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)
 		{
@@ -319,6 +323,9 @@ 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_ex_func(str,num,file,line);
@@ -338,6 +345,9 @@ void *CRYPTO_realloc_clean(void *str, int old_len, int num, const char *file,
 
 	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=malloc_ex_func(num,file,line);