diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index c1d0295..2f1fdb6 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -3451,7 +3451,8 @@
 			    // "varname[]" is an expression.
 			    *p == '['
 			    // "varname.key" is an expression.
-			 || (*p == '.' && ASCII_ISALPHA(p[1]))))
+			 || (*p == '.' && (ASCII_ISALPHA(p[1])
+							     || p[1] == '_'))))
 	    {
 		char_u	*after = eap->cmd;