diff --git a/du3/program.c b/du3/program.c
index 2587523..a2a818a 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -45,6 +45,11 @@ float pop_stack(struct stack* mystack,const char input[])
     assert(mystack->size>1);
     float val1=mystack->values[mystack->size-2];
     float val2=mystack->values[mystack->size-1];
+    if(val2==0)
+    {
+	    printf("division by zero\n");
+	    return 0;
+    }
     switch (input[0])
     {
     case '+':