diff --git a/src/window.c b/src/window.c
index f0a4265..0c0fb30 100644
--- a/src/window.c
+++ b/src/window.c
@@ -3143,7 +3143,7 @@
 
 /*
  * Get index of tab page "tp".  First one has index 1.
- * When not found returns number of tab pages.
+ * When not found returns number of tab pages plus one.
  */
     int
 tabpage_index(ftp)