diff --git a/src/eval.c b/src/eval.c
index 6ba2dd8..bc7f22a 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -21064,7 +21064,8 @@
     char_u *name;    /* points to start of variable name */
     int    new_var;  /* TRUE when creating the variable */
 {
-    if (!(vim_strchr((char_u *)"wbs", name[0]) != NULL && name[1] == ':')
+    /* Allow for w: b: s: and t:. */
+    if (!(vim_strchr((char_u *)"wbst", name[0]) != NULL && name[1] == ':')
 	    && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':')
 						     ? name[2] : name[0]))
     {