diff --git a/src/mfast/coder/encoder_v2/fast_encoder_core.h b/src/mfast/coder/encoder_v2/fast_encoder_core.h
index 6f669157..345627ae 100644
--- a/src/mfast/coder/encoder_v2/fast_encoder_core.h
+++ b/src/mfast/coder/encoder_v2/fast_encoder_core.h
@@ -470,6 +470,11 @@ void fast_encoder_core::encode_field(const T &ext_ref, default_operator_tag,
     return;
   }
 
+  if (ext_ref.optional() && !ext_ref.present()) {
+    pmap.set_next_bit(false);
+    return;
+  }
+
   pmap.set_next_bit(true);
   if (!ext_ref.present()) {
     //  A NULL indicates that the value is absent and the state of the previous
diff --git a/tests/encoder_decoder_test.cpp b/tests/encoder_decoder_test.cpp
index 8c3d1d87..96271e48 100644
--- a/tests/encoder_decoder_test.cpp
+++ b/tests/encoder_decoder_test.cpp
@@ -225,3 +225,23 @@ TEST_CASE("simple field group optional encoder/decoder","[field_group_optional_e
         REQUIRE(test_case.decoding("\xF0\x85\x82\xC0\x81\x81\x82\x8B",test_5.cref(),true));
     }
 }
+
+TEST_CASE("simple optional field with default value encoder/decoder","[optional_field_with_default_value_encoder_decoder]")
+{
+    fast_test_coding_case<simple12::templates_description> test_case;
+
+    SECTION("encode fields")
+    {
+        simple12::Test_6 test_6;
+        simple12::Test_6_mref test_6_mref = test_6.mref();
+        test_6_mref.set_field_6_2().as(1);
+        // \xD0 : 1110 : OK
+        // 1 : Stop Bit.
+        // 1 : Set Template Id.
+        // 0 : Not Set Field field_6_1
+        // 1 : Set field_6_2
+        REQUIRE(test_case.encoding(test_6.cref(),"\xD0\x86\x82",true));
+        test_6_mref.set_field_6_1().as(1);
+        REQUIRE(test_case.decoding("\xD0\x86\x82",test_6.cref(),true));
+    }
+}
diff --git a/tests/encoder_decoder_test_v2.cpp b/tests/encoder_decoder_test_v2.cpp
index 5261a673..4846e84a 100644
--- a/tests/encoder_decoder_test_v2.cpp
+++ b/tests/encoder_decoder_test_v2.cpp
@@ -226,3 +226,23 @@ TEST_CASE("simple field group optional encoder_v2/decoder_v2","[field_group_opti
         REQUIRE(test_case.decoding("\xF0\x85\x82\xC0\x81\x81\x82\x8B",test_5.cref(),true));
     }
 }
+
+TEST_CASE("simple optional field with default value encoder_v2/decoder_v2","[optional_field_with_default_value_encoder_v2/decoder_v2]")
+{
+    fast_test_coding_case_v2<simple12::templates_description> test_case;
+
+    SECTION("encode field")
+    {
+        simple12::Test_6 test_6;
+        simple12::Test_6_mref test_6_mref = test_6.mref();
+        test_6_mref.set_field_6_2().as(1);
+        // \xD0 : 1110 : OK
+        // 1 : Stop Bit.
+        // 1 : Set Template Id.
+        // 0 : Not Set Field field_6_1
+        // 1 : Set field_6_2
+        REQUIRE(test_case.encoding(test_6.cref(),"\xD0\x86\x82",true));
+        test_6_mref.set_field_6_1().as(1);
+        REQUIRE(test_case.decoding("\xD0\x86\x82",test_6.cref(),true));
+    }
+}
diff --git a/tests/encoder_operator_test.cpp b/tests/encoder_operator_test.cpp
index 288828ae..9a98ac95 100644
--- a/tests/encoder_operator_test.cpp
+++ b/tests/encoder_operator_test.cpp
@@ -405,7 +405,7 @@ TEST_CASE("test the encoding of fast operator default","[operator_default_encode
 
     inst.prev_value().defined(false); // reset the previous value to undefined again
 
-    REQUIRE( encode_ext_cref("\xC0\x80",
+    REQUIRE( encode_ext_cref("\x80",
                                  ext_cref<uint64_cref, default_operator_tag, optional_with_initial_value_tag>(result),
                                  PRESERVE_PREVIOUS_VALUE, &allocator ) );
   }
diff --git a/tests/simple12.xml b/tests/simple12.xml
index 27b491da..2465c03d 100644
--- a/tests/simple12.xml
+++ b/tests/simple12.xml
@@ -32,4 +32,15 @@
             <uInt32 name="field_5_5" id="54" presence="optional"><copy/></uInt32>
         </group>
     </template>
+    <template name="Test_6" id="6">
+        <uInt32 name="field_6_1" id="61" presence="optional">
+            <default value="1"/>
+        </uInt32>
+        <uInt32 name="field_6_2" id="62" presence="optional">
+            <copy/>
+        </uInt32>
+        <uInt32 name="field_6_3" id="63">
+            <default value="1"/>
+        </uInt32>
+    </template>
 </templates>