diff --git a/src/eval.c b/src/eval.c
index 7ce739c..1c2bd61 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -9216,6 +9216,9 @@
     int		error = FALSE;
     garray_T	ga;
 
+    if (argvars[0].v_type == VAR_SPECIAL
+	    && argvars[0].vval.v_number == (isTrue ? VVAL_TRUE : VV_FALSE))
+	return;
     if (argvars[0].v_type != VAR_NUMBER
 	    || (get_tv_number_chk(&argvars[0], &error) == 0) == isTrue
 	    || error)