1 files changed, 3 insertions, 0 deletions
diff --git a/safe.c b/safe.c
index e351579132..ebe62f4206 100644
--- a/safe.c
+++ b/safe.c
@@ -66,6 +66,9 @@ safe_setter(VALUE val)
 		 "tried to downgrade safe level from %d to %d",
 		 th->safe_level, level);
     }
+    if (level == 3) {
+	rb_warning("$SAFE=3 does no sandboxing; you might want to use $SAFE=4");
+    }
     if (level > SAFE_LEVEL_MAX) {
 	level = SAFE_LEVEL_MAX;
     }