diff --git a/test/system/test_interactions/const_custom_type.yml b/test/system/test_interactions/const_custom_type.yml
new file mode 100644
index 0000000..c7c1890
--- /dev/null
+++ b/test/system/test_interactions/const_custom_type.yml
@@ -0,0 +1,68 @@
+# =========================================================================
+#   CMock - Automatic Mock Generation for C
+#   ThrowTheSwitch.org
+#   Copyright (c) 2007-26 Mike Karlesky, Mark VanderVoord, & Greg Williams
+#   SPDX-License-Identifier: MIT
+# =========================================================================
+
+---
+:cmock:
+  :plugins:
+  - # none
+
+:systest:
+  :types: |
+    typedef enum {
+        MyTypeA,
+        MyTypeB,
+        MyTypeC,
+    } MyType_t;
+
+  :mockable: |
+    int myFunc(const MyType_t t_MyType);
+
+  :source:
+    :header: |
+      int exercise(const MyType_t t_MyType);
+
+    :code: |
+      int exercise(const MyType_t t_MyType)
+      {
+        return myFunc(t_MyType);
+      }
+
+  :tests:
+    :common: |
+      void setUp(void) {}
+      void tearDown(void) {}
+
+    :units:
+    - :pass: TRUE
+      :should: 'compile and pass when the correct enum value is passed and return value matches'
+      :code: |
+        test()
+        {
+          myFunc_ExpectAndReturn(MyTypeB, 42);
+          TEST_ASSERT_EQUAL(42, exercise(MyTypeB));
+        }
+
+    - :pass: FALSE
+      :should: 'fail when the wrong enum value is passed'
+      :code: |
+        test()
+        {
+          myFunc_ExpectAndReturn(MyTypeB, 42);
+          exercise(MyTypeC);
+        }
+
+    - :pass: TRUE
+      :should: 'pass when called with a const MyType_t variable'
+      :code: |
+        test()
+        {
+          const MyType_t val = MyTypeA;
+          myFunc_ExpectAndReturn(MyTypeA, 0);
+          TEST_ASSERT_EQUAL(0, exercise(val));
+        }
+
+...
diff --git a/test/unit/cmock_generator_plugin_expect_a_test.rb b/test/unit/cmock_generator_plugin_expect_a_test.rb
index 8d12c2e..f649ba1 100644
--- a/test/unit/cmock_generator_plugin_expect_a_test.rb
+++ b/test/unit/cmock_generator_plugin_expect_a_test.rb
@@ -223,6 +223,26 @@ describe CMockGeneratorPluginExpect, "Verify CMockGeneratorPluginExpect Module W
     assert_equal(expected, returned)
   end
 
+  it "preserve const on non-pointer custom type in mock function declaration but drop it from struct field" do
+    function = {
+      :name        => "myFunc",
+      :args        => [{ :name => "t_MyType", :type => "MyType_t", :ptr? => false, :const? => true, :const_ptr? => false }],
+      :args_string => "const MyType_t t_MyType",
+      :args_call   => "t_MyType",
+      :return      => test_return[:int]
+    }
+    # struct field uses arg[:type] directly — no const, so the field stays writable
+    expected_typedef = "  int ReturnVal;\n" \
+                       "  MyType_t Expected_t_MyType;\n"
+    assert_equal(expected_typedef, @cmock_generator_plugin_expect.instance_typedefs(function))
+
+    # function declaration uses args_string — const MyType_t must appear in the C signature
+    expected_decl = "#define myFunc_Expect(t_MyType) TEST_FAIL_MESSAGE(\"myFunc requires _ExpectAndReturn\");\n" \
+                    "#define myFunc_ExpectAndReturn(t_MyType, cmock_retval) myFunc_CMockExpectAndReturn(__LINE__, t_MyType, cmock_retval)\n" \
+                    "void myFunc_CMockExpectAndReturn(UNITY_LINE_TYPE cmock_line, const MyType_t t_MyType, int cmock_to_return);\n"
+    assert_equal(expected_decl, @cmock_generator_plugin_expect.mock_function_declarations(function))
+  end
+
   it "store const-pointer return value without trailing const in typedef struct field (for writability)" do
     int_ptr_const_return = { :type => "int*", :name => "cmock_to_return", :ptr? => true,
                              :const? => false, :const_ptr? => true, :void? => false,
diff --git a/test/unit/cmock_header_parser_test.rb b/test/unit/cmock_header_parser_test.rb
index 1d632f7..50615c1 100644
--- a/test/unit/cmock_header_parser_test.rb
+++ b/test/unit/cmock_header_parser_test.rb
@@ -3139,4 +3139,33 @@ describe CMockHeaderParser, "Verify CMockHeaderParser Module" do
     assert_equal(expected, @parser.parse("module", source)[:functions])
   end
 
+  it "preserve const on non-pointer custom type arguments (e.g. const MyType_t)" do
+    source = "int myFunc(const MyType_t t_MyType);\n"
+
+    expected = [{ :var_arg => nil,
+                  :name    => "myFunc",
+                  :unscoped_name => "myFunc",
+                  :namespace => [],
+                  :class => nil,
+                  :return  => { :type       => "int",
+                                :name       => 'cmock_to_return',
+                                :ptr?       => false,
+                                :const?     => false,
+                                :const_ptr? => false,
+                                :str        => "int cmock_to_return",
+                                :void?      => false
+                              },
+                  :modifier      => "",
+                  :contains_ptr? => false,
+                  :args => [
+                    { :type => "MyType_t", :name => "t_MyType", :ptr? => false, :string? => false,
+                      :const? => true, :const_ptr? => false }
+                  ],
+                  :args_string => "const MyType_t t_MyType",
+                  :args_call   => "t_MyType"
+                }]
+
+    assert_equal(expected, @parser.parse("module", source)[:functions])
+  end
+
 end