diff --git a/lib/bundled_gems.rb b/lib/bundled_gems.rb
index 873377dfd1..3967511cd1 100644
--- a/lib/bundled_gems.rb
+++ b/lib/bundled_gems.rb
@@ -103,9 +103,6 @@ module Gem::BUNDLED_GEMS
       return
     end
     return if WARNED[name]
-    # Ignore to warn like "bigdecimal/util" feature.
-    # It should be better to warn it, but it is difficult to cover all of target features.
-    return unless SINCE[name]
     WARNED[name] = true
     if gem == true
       gem = name