diff --git a/cv7/program.c b/cv7/program.c
index 453347c..5128db9 100644
--- a/cv7/program.c
+++ b/cv7/program.c
@@ -21,7 +21,7 @@ struct tree* read_tree()
     memset(buffer,0,SIZE);
     char* r = fgets(buffer,SIZE,stdin);    
 
-    assert(r);
+    if(r==NULL) return NULL;
 
     if(buffer[0]=='\n')
         return NULL;
@@ -140,4 +140,3 @@ int main(void)
 }
 
 
-