diff --git a/lib/irb/ext/save-history.rb b/lib/irb/ext/save-history.rb
index 7acaebe36a..ad954c3558 100644
--- a/lib/irb/ext/save-history.rb
+++ b/lib/irb/ext/save-history.rb
@@ -107,9 +107,9 @@ module IRB
           raise
         end
 
-        if File.exist?(history_file) && @loaded_history_mtime &&
+        if File.exist?(history_file) &&
            File.mtime(history_file) != @loaded_history_mtime
-          history = history[@loaded_history_lines..-1]
+          history = history[@loaded_history_lines..-1] if @loaded_history_lines
           append_history = true
         end
 
diff --git a/test/irb/test_history.rb b/test/irb/test_history.rb
index 81b7fe8679..38a002d319 100644
--- a/test/irb/test_history.rb
+++ b/test/irb/test_history.rb
@@ -158,6 +158,28 @@ module TestIRB
       end
     end
 
+    def test_history_concurrent_use_not_present
+      backup_home = ENV["HOME"]
+      backup_xdg_config_home = ENV.delete("XDG_CONFIG_HOME")
+      IRB.conf[:SAVE_HISTORY] = 1
+      Dir.mktmpdir("test_irb_history_#{$$}") do |tmpdir|
+        ENV["HOME"] = tmpdir
+        io = TestInputMethod.new
+        io.class::HISTORY.clear
+        io.load_history
+        io.class::HISTORY.concat(%w"line1 line2")
+
+        history_file = IRB.rc_file("_history")
+        assert !File.file?(history_file)
+        File.write(history_file, "line0\n")
+        io.save_history
+        assert_equal(%w"line0 line1 line2", File.read(history_file).split)
+      end
+    ensure
+      ENV["HOME"] = backup_home
+      ENV["XDG_CONFIG_HOME"] = backup_xdg_config_home
+    end
+
     private
 
     def assert_history(expected_history, initial_irb_history, input)