diff --git a/src/evalfunc.c b/src/evalfunc.c
index 110935d..1764f41 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1975,7 +1975,7 @@
     int		copyID;
 
     if (argvars[1].v_type != VAR_UNKNOWN)
-	noref = (int)tv_get_number_chk(&argvars[1], NULL);
+	noref = (int)tv_get_bool_chk(&argvars[1], NULL);
     if (noref < 0 || noref > 1)
 	emsg(_(e_invarg));
     else