diff --git a/node.h b/node.h
index dff7613936..bfc7493e50 100644
--- a/node.h
+++ b/node.h
@@ -74,7 +74,7 @@ RUBY_SYMBOL_EXPORT_END
 #define NODE_LSHIFT (NODE_TYPESHIFT+7)
 #define NODE_LMASK  (((SIGNED_VALUE)1<<(sizeof(VALUE)*CHAR_BIT-NODE_LSHIFT))-1)
 
-#define nd_line(n) (int)(((SIGNED_VALUE)(n)->flags)>>NODE_LSHIFT)
+#define nd_line(n) (int)((n) ? ((SIGNED_VALUE)(n)->flags)>>NODE_LSHIFT : -1)
 #define nd_set_line(n,l) \
     (n)->flags=(((n)->flags&~((VALUE)(-1)<<NODE_LSHIFT))|((VALUE)((l)&NODE_LMASK)<<NODE_LSHIFT))