diff --git a/kernel/common/env.rb b/kernel/common/env.rb
index 22b465e321..5f4667a373 100644
--- a/kernel/common/env.rb
+++ b/kernel/common/env.rb
@@ -57,7 +57,11 @@ def each
 
     def delete(key)
       existing_value = self[key]
-      self[key] = nil if existing_value
+      if existing_value
+        self[key] = nil
+      elsif block_given?
+        yield key
+      end
       existing_value
     end