diff --git a/lang/number.c b/lang/number.c
index 702cee9..fc01c3d 100644
--- a/lang/number.c
+++ b/lang/number.c
@@ -48,6 +48,7 @@
 	vm_stack_set(state, 0, number_create(added));
 	vm_stack_drop(state, 1);
 	object_drop(&arg1);
+	numB = NULL;
 }
 
 static void number_minus(VmState state, Object obj) {
@@ -63,6 +64,7 @@
 	vm_stack_set(state, 0, number_create(subbed));
 	vm_stack_drop(state, 1);
 	object_drop(&arg1);
+	numB = NULL;
 }
 
 static struct object_call calls[] = {{.name = "Add", .handler = number_add},