diff --git a/crypto/rsa/rsa_oaep.c b/crypto/rsa/rsa_oaep.c
index 8da765e4d736a5c8d6cf44a721135cfb8f626f23..e6d98c5bdbdafdf9ebf2731708fb662d965b41c3 100644
--- a/crypto/rsa/rsa_oaep.c
+++ b/crypto/rsa/rsa_oaep.c
@@ -164,8 +164,10 @@ int MGF1(unsigned char *mask, long len,
 
     for (i = 0; outlen < len; i++)
 	{
-	cnt[0] = (i >> 24) & 255, cnt[1] = (i >> 16) & 255,
-	  cnt[2] = (i >> 8) & 255, cnt[3] = i & 255;
+	cnt[0] = (unsigned char)((i >> 24) & 255);
+	cnt[1] = (unsigned char)((i >> 16) & 255);
+	cnt[2] = (unsigned char)((i >> 8)) & 255;
+	cnt[3] = (unsigned char)(i & 255);
 	EVP_DigestInit(&c,EVP_sha1());
 	EVP_DigestUpdate(&c, seed, seedlen);
 	EVP_DigestUpdate(&c, cnt, 4);