diff --git a/du1/program.c b/du1/program.c
index 2122f87..4307bb7 100644
--- a/du1/program.c
+++ b/du1/program.c
@@ -29,7 +29,7 @@ int main (){
 		}
 		else{
 			for(int i = 0; i < 100; i++){
-				if(c[i] == '\n') break;
+				if(c[i] == '\n' || c[i] == "\0") break;
 				if(isupper(c[i])) {
                     printf("%c", tolower(c[i]));
                 }