diff --git a/.gitignore b/.gitignore
index 5acb669..3bfd071 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 build
 .vscode
+*.bak
diff --git a/src/mfast/coder/encoder/fast_encoder.cpp b/src/mfast/coder/encoder/fast_encoder.cpp
index 35b2205..0e834ac 100644
--- a/src/mfast/coder/encoder/fast_encoder.cpp
+++ b/src/mfast/coder/encoder/fast_encoder.cpp
@@ -195,8 +195,11 @@ void fast_encoder_impl::visit(message_cref cref, bool force_reset) {
   aggregate_cref message(cref.field_storage(0), instruction);
 
   for (auto &&field : message)
-    if (field.present() || field.instruction()->field_operator() == operator_none)
+  {
+    const operator_enum_t op = field.instruction()->field_operator();
+    if (field.present() || op == operator_none || op == operator_default || (op == operator_constant && field.instruction()->pmap_size() > 0))
       apply_accessor(*this, field);
+  }
 
   pmap.commit();
 }
diff --git a/src/mfast/field_mref.h b/src/mfast/field_mref.h
index d33dce8..553bee0 100644
--- a/src/mfast/field_mref.h
+++ b/src/mfast/field_mref.h
@@ -73,6 +73,7 @@ template <typename T> void field_mref::as(T value) {
     static_cast<uint64_mref>(*this).as(static_cast<uint64_t>(value));
     break;
   case field_type_decimal:
+  case field_type_exponent: 
     static_cast<decimal_mref>(*this).as(value);
     break;
   default:
diff --git a/tests/coder_test.cpp b/tests/coder_test.cpp
index 749ea3a..f9c0d5e 100644
--- a/tests/coder_test.cpp
+++ b/tests/coder_test.cpp
@@ -404,3 +404,24 @@ TEST_CASE("test fast coder for a template with zero segment size", "[segment_pma
 }
 
 
+TEST_CASE("test fast coder without code generation for a simple template with constant and default","[manual_reset_test]")
+{
+  fast_coding_test_case test_case (
+    "<?xml version=\" 1.0 \"?>\n"
+    "<templates xmlns=\"http://www.fixprotocol.org/ns/template-definition\" "
+    "templateNs=\"http://www.fixprotocol.org/ns/templates/sample\" ns=\"http://www.fixprotocol.org/ns/fix\">\n"
+    "<template name=\"Test\" id=\"1\">\n"
+    "<uInt32 name=\"field1\" id=\"11\"><constant value=\"77\"/></uInt32>\n"
+    "<uInt32 name=\"field2\" id=\"12\" presence=\"optional\"><default value=\"50\"/></uInt32>\n"
+    "<uInt32 name=\"field3\" id=\"13\" presence=\"optional\"><constant value=\"89\"/></uInt32>\n"
+    "</template>\n"
+    "</templates>\n");
+
+  debug_allocator alloc;
+  message_type msg(&alloc, test_case.template_with_id(1));
+  message_mref msg_ref = msg.mref();
+
+  // Not setting fields...
+  REQUIRE(test_case.encoding(msg_ref, "\xa0\x80"));
+  REQUIRE(test_case.decoding("\xa0\x80", msg_ref));
+}