diff --git a/lib/irb/ext/history.rb b/lib/irb/ext/history.rb
index 62363b13f4..43c3e4dbf3 100644
--- a/lib/irb/ext/history.rb
+++ b/lib/irb/ext/history.rb
@@ -22,7 +22,7 @@ module IRB # :nodoc:
     def set_last_value(value)
       _set_last_value(value)
 
-      if @eval_history
+      if defined?(@eval_history) && @eval_history
         @eval_history_values.push @line_no, @last_value
         @workspace.evaluate self, "__ = IRB.CurrentContext.instance_eval{@eval_history_values}"
       end
@@ -30,6 +30,7 @@ module IRB # :nodoc:
       @last_value
     end
 
+    remove_method :eval_history= if method_defined?(:eval_history=)
     # The command result history limit.
     attr_reader :eval_history
     # Sets command result history limit.
diff --git a/lib/irb/ext/save-history.rb b/lib/irb/ext/save-history.rb
index 8ee5d269e6..9aeb5dee0c 100644
--- a/lib/irb/ext/save-history.rb
+++ b/lib/irb/ext/save-history.rb
@@ -27,7 +27,7 @@ module IRB
       IRB.conf[:SAVE_HISTORY]
     end
 
-    remove_method :save_history= if respond_to?(:save_history=)
+    remove_method :save_history= if method_defined?(:save_history=)
     # Sets <code>IRB.conf[:SAVE_HISTORY]</code> to the given +val+ and calls
     # #init_save_history with this context.
     #
diff --git a/lib/irb/ext/use-loader.rb b/lib/irb/ext/use-loader.rb
index cc71706671..cb10e8a254 100644
--- a/lib/irb/ext/use-loader.rb
+++ b/lib/irb/ext/use-loader.rb
@@ -20,10 +20,12 @@ end
 
 module IRB
   module ExtendCommandBundle
+    remove_method :irb_load if method_defined?(:irb_load)
     # Loads the given file similarly to Kernel#load, see IrbLoader#irb_load
     def irb_load(*opts, &b)
       ExtendCommand::Load.execute(irb_context, *opts, &b)
     end
+    remove_method :irb_require if method_defined?(:irb_require)
     # Loads the given file similarly to Kernel#require
     def irb_require(*opts, &b)
       ExtendCommand::Require.execute(irb_context, *opts, &b)
@@ -44,6 +46,7 @@ module IRB
 
     alias use_loader? use_loader
 
+    remove_method :use_loader= if method_defined?(:use_loader=)
     # Sets IRB.conf[:USE_LOADER]
     #
     # See #use_loader for more information.