diff --git a/gapic/schema/wrappers.py b/gapic/schema/wrappers.py
index aa474e0e4e..c4c9e6bec0 100644
--- a/gapic/schema/wrappers.py
+++ b/gapic/schema/wrappers.py
@@ -94,7 +94,20 @@ def map(self) -> bool:
         return bool(self.repeated and self.message and self.message.map)
 
     @utils.cached_property
-    def mock_value_original_type(self) -> Union[bool, str, bytes, int, float, List[Any], None]:
+    def mock_value_original_type(self) -> Union[bool, str, bytes, int, float, Dict[str, Any], List[Any], None]:
+        # Return messages as dicts and let the message ctor handle the conversion.
+        if self.message:
+            if self.map:
+                # Not worth the hassle, just return an empty map.
+                return {}
+
+            msg_dict = {
+                f.name: f.mock_value_original_type
+                for f in self.message.fields.values()
+            }
+
+            return [msg_dict] if self.repeated else msg_dict
+
         answer = self.primitive_mock() or None
 
         # If this is a repeated field, then the mock answer should
@@ -173,7 +186,7 @@ def primitive_mock(self, suffix: int = 0) -> Union[bool, str, bytes, int, float,
         answer: Union[bool, str, bytes, int, float, List[Any], None] = None
 
         if not isinstance(self.type, PrimitiveType):
-            raise TypeError(f"'inner_mock_as_original_type' can only be used for"
+            raise TypeError(f"'primitive_mock' can only be used for "
                 f"PrimitiveType, but type is {self.type}")
 
         else:
diff --git a/tests/fragments/test_non_primitive_body.proto b/tests/fragments/test_non_primitive_body.proto
new file mode 100644
index 0000000000..f322a747a4
--- /dev/null
+++ b/tests/fragments/test_non_primitive_body.proto
@@ -0,0 +1,53 @@
+// Copyright (C) 2021  Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package google.fragment;
+
+import "google/api/client.proto";
+import "google/api/annotations.proto";
+import "google/api/field_behavior.proto";
+
+service SmallCompute {
+  option (google.api.default_host) = "my.example.com";
+
+  rpc MyMethod(MethodRequest) returns (MethodResponse) {
+    option (google.api.http) = {
+      body: "method_body"
+      post: "/computation/v1/first_name/{first_name}/last_name/{last_name}"
+    };
+  };
+}
+
+message SerialNumber {
+  int32 number = 1;
+}
+
+message MethodRequest {
+  message MethodBody {
+    int32 mass_kg = 1;
+    int32 length_cm = 2;
+    repeated SerialNumber serial_numbers = 3;
+    map<string, SerialNumber> word_associations = 4;
+  }
+
+  string first_name = 1 [(google.api.field_behavior) = REQUIRED];
+  string last_name = 2 [(google.api.field_behavior) = REQUIRED];
+  MethodBody method_body = 3 [(google.api.field_behavior) = REQUIRED];
+}
+
+message MethodResponse {
+  string name = 1;
+}
\ No newline at end of file
diff --git a/tests/unit/schema/wrappers/test_field.py b/tests/unit/schema/wrappers/test_field.py
index f823104e77..151b2762b8 100644
--- a/tests/unit/schema/wrappers/test_field.py
+++ b/tests/unit/schema/wrappers/test_field.py
@@ -241,6 +241,7 @@ def test_mock_value_map():
         label=3,
         type='TYPE_MESSAGE',
     )
+
     assert field.mock_value == "{'key_value': 'value_value'}"
 
 
@@ -290,7 +291,7 @@ def test_mock_value_message():
     assert field.mock_value == 'bogus.Message(foo=324)'
 
 
-def test_mock_value_original_type_message_errors():
+def test_mock_value_original_type_message():
     subfields = collections.OrderedDict((
         ('foo', make_field(name='foo', type='TYPE_INT32')),
         ('bar', make_field(name='bar', type='TYPE_STRING'))
@@ -307,14 +308,39 @@ def test_mock_value_original_type_message_errors():
         nested_enums={},
         nested_messages={},
     )
+
     field = make_field(
         type='TYPE_MESSAGE',
         type_name='bogus.Message',
         message=message,
     )
 
+    mock = field.mock_value_original_type
+
+    assert mock == {"foo": 324, "bar": "bar_value"}
+
+    # Messages by definition aren't primitive
     with pytest.raises(TypeError):
-        mock = field.mock_value_original_type
+        field.primitive_mock()
+
+    # Special case for map entries
+    entry_msg = make_message(
+        name='MessageEntry',
+        fields=(
+            make_field(name='key', type='TYPE_STRING'),
+            make_field(name='value', type='TYPE_STRING'),
+        ),
+        options=descriptor_pb2.MessageOptions(map_entry=True),
+    )
+    entry_field = make_field(
+        name="messages",
+        type_name="stuff.MessageEntry",
+        message=entry_msg,
+        label=3,
+        type='TYPE_MESSAGE',
+    )
+
+    assert entry_field.mock_value_original_type == {}
 
 
 def test_mock_value_recursive():