diff --git a/1-15.c b/1-15.c
index 0463d49..54f3b57 100644
--- a/1-15.c
+++ b/1-15.c
@@ -7,4 +7,5 @@ int main(){
   for (fahr=300; fahr>=0; fahr-=20){
     printf("%3d %6.1f\n", fahr, fahr_to_celsius(fahr));
   }
+  return 0;
 }