diff --git a/crypto/buffer/buffer.c b/crypto/buffer/buffer.c
index a6b590c3b..d4a4ce43b 100644
--- a/crypto/buffer/buffer.c
+++ b/crypto/buffer/buffer.c
@@ -179,7 +179,7 @@ int BUF_MEM_grow_clean(BUF_MEM *str, size_t len)
 	return(len);
 	}
 
-void BUF_reverse(unsigned char *out, unsigned char *in, size_t size)
+void BUF_reverse(unsigned char *out, const unsigned char *in, size_t size)
 	{
 	size_t i;
 	if (in)
diff --git a/crypto/buffer/buffer.h b/crypto/buffer/buffer.h
index 178e41828..f8da32b48 100644
--- a/crypto/buffer/buffer.h
+++ b/crypto/buffer/buffer.h
@@ -88,7 +88,7 @@ int	BUF_MEM_grow_clean(BUF_MEM *str, size_t len);
 char *	BUF_strdup(const char *str);
 char *	BUF_strndup(const char *str, size_t siz);
 void *	BUF_memdup(const void *data, size_t siz);
-void	BUF_reverse(unsigned char *out, unsigned char *in, size_t siz);
+void	BUF_reverse(unsigned char *out, const unsigned char *in, size_t siz);
 
 /* safe string functions */
 size_t BUF_strlcpy(char *dst,const char *src,size_t siz);