diff --git a/src/option.c b/src/option.c
index 4ad558a..5bcb33e 100644
--- a/src/option.c
+++ b/src/option.c
@@ -3247,7 +3247,7 @@
 static char *(p_fcl_values[]) = {"all", NULL};
 #endif
 #ifdef FEAT_INS_EXPAND
-static char *(p_cot_values[]) = {"menu", "menuone", "longest", "preview", "noinsert", "noselect", NULL};
+static char *(p_cot_values[]) = {"menu", "menuone", "longest", "preview", "popup", "noinsert", "noselect", NULL};
 # ifdef BACKSLASH_IN_FILENAME
 static char *(p_csl_values[]) = {"slash", "backslash", NULL};
 # endif