diff --git a/libekmfweb/ekmfweb.c b/libekmfweb/ekmfweb.c
index 11106bd0..7d880633 100644
--- a/libekmfweb/ekmfweb.c
+++ b/libekmfweb/ekmfweb.c
@@ -4548,8 +4548,9 @@ out:
  */
 static char *_ekmf_base64_encode(const unsigned char *data, size_t data_size)
 {
-	int outlen, len;
+	size_t outlen;
 	char *out;
+	int len;
 
 	outlen = (data_size / 3) * 4;
 	if (data_size % 3 > 0)
@@ -4560,7 +4561,7 @@ static char *_ekmf_base64_encode(const unsigned char *data, size_t data_size)
 		return NULL;
 
 	len = EVP_EncodeBlock((unsigned char *)out, data, data_size);
-	if (len != outlen) {
+	if (len < 0 || (size_t)len != outlen) {
 		free(out);
 		return NULL;
 	}
diff --git a/libekmfweb/utilities.c b/libekmfweb/utilities.c
index a8cc5350..792693c6 100644
--- a/libekmfweb/utilities.c
+++ b/libekmfweb/utilities.c
@@ -106,7 +106,7 @@ int decode_base64url(unsigned char *output, size_t *outlen,
 
 	len = EVP_DecodeBlock((unsigned char *)padded_output,
 			      (unsigned char *)padded_input, padded_inlen);
-	if (len != (int)padded_inlen * 3 / 4) {
+	if ((size_t)len != padded_inlen * 3 / 4) {
 		rc = -EIO;
 		goto out;
 	}