diff --git a/sys/src/libmp/port/strtomp.c b/sys/src/libmp/port/strtomp.c
index 51d462101..b0b7d2898 100644
--- a/sys/src/libmp/port/strtomp.c
+++ b/sys/src/libmp/port/strtomp.c
@@ -240,13 +240,13 @@ strtomp(char *a, char **pp, int base, mpint *b)
 		return nil;
 	}
 
+	if(pp != nil)
+		*pp = e;
+
 	// if no characters parsed, there wasn't a number to convert
 	if(e == a)
 		return nil;
 
-	if(pp != nil)
-		*pp = e;
-
 	b->sign = sign;
 	return mpnorm(b);
 }