diff --git a/library/x509.c b/library/x509.c
index 5e6062bfa5..fbee2c54df 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -480,7 +480,7 @@ int x509_get_name( unsigned char **p, const unsigned char *end,
     }
 }
 
-static int x509_parse_int(unsigned char **p, unsigned n, int *res){
+static int x509_parse_int(unsigned char **p, size_t n, int *res){
     *res = 0;
     for( ; n > 0; --n ){
         if( ( **p < '0') || ( **p > '9' ) ) return POLARSSL_ERR_X509_INVALID_DATE;