diff --git a/src/eval.c b/src/eval.c
index 699598b..1216dc6 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -362,6 +362,7 @@
     {VV_NAME("operator",	 VAR_STRING), VV_RO},
     {VV_NAME("searchforward",	 VAR_NUMBER), 0},
     {VV_NAME("oldfiles",	 VAR_LIST), 0},
+    {VV_NAME("windowid",	 VAR_NUMBER), VV_RO},
 };
 
 /* shorthand */