diff --git a/lib/mprintf.c b/lib/mprintf.c
index 2f7f31e29..3f74f26f5 100644
--- a/lib/mprintf.c
+++ b/lib/mprintf.c
@@ -763,7 +763,7 @@ static int dprintf_formatf(
       /* Decimal integer.  */
       base = 10;
 
-      is_neg = p->data.num.as_signed < 0;
+      is_neg = (p->data.num.as_signed < (mp_intmax_t)0);
       if(is_neg) {
         /* signed_num might fail to hold absolute negative minimum by 1 */
         signed_num = p->data.num.as_signed + (mp_intmax_t)1;