diff --git a/spec/spectator/mocks/mock_spec.cr b/spec/spectator/mocks/mock_spec.cr
index fbf2b4e..b469dbb 100644
--- a/spec/spectator/mocks/mock_spec.cr
+++ b/spec/spectator/mocks/mock_spec.cr
@@ -1,43 +1,11 @@
 require "../../spec_helper"
 
-class MockedClass
-  getter method1 = 42
-
-  def method2
-    :original
-  end
-
-  def method3
-    "original"
-  end
-
-  def instance_variables
-    [{{@type.instance_vars.map(&.name.symbolize).splat}}]
-  end
-end
-
-struct MockedStruct
-  getter method1 = 42
-
-  def method2
-    :original
-  end
-
-  def method3
-    "original"
-  end
-
-  def instance_variables
-    [{{@type.instance_vars.map(&.name.symbolize).splat}}]
-  end
-end
-
 Spectator.describe Spectator::Mock do
   let(stub1) { Spectator::ValueStub.new(:method1, 777) }
   let(stub2) { Spectator::ValueStub.new(:method2, :override) }
   let(stub3) { Spectator::ValueStub.new(:method3, "stubbed") }
 
-  describe "#define_subclass" do
+  describe "#define_subtype" do
     class Thing
       def method1
         42
@@ -52,7 +20,7 @@ Spectator.describe Spectator::Mock do
       end
     end
 
-    Spectator::Mock.define_subclass(Thing, MockThing, :mock_name, method1: 123) do
+    Spectator::Mock.define_subtype(:class, Thing, MockThing, :mock_name, method1: 123) do
       stub def method2
         :stubbed
       end
@@ -102,11 +70,24 @@ Spectator.describe Spectator::Mock do
   end
 
   describe "#inject" do
-    # For some reason, `inject` can't find the types.
-    # Their definitions are outside of the spec as a workaround.
-
     context "with a class" do
-      Spectator::Mock.inject(MockedClass, :mock_name, method1: 123) do
+      class MockedClass
+        getter method1 = 42
+
+        def method2
+          :original
+        end
+
+        def method3
+          "original"
+        end
+
+        def instance_variables
+          [{{@type.instance_vars.map(&.name.symbolize).splat}}]
+        end
+      end
+
+      Spectator::Mock.inject(:class, MockedClass, :mock_name, method1: 123) do
         stub def method2
           :stubbed
         end
@@ -163,7 +144,23 @@ Spectator.describe Spectator::Mock do
     end
 
     context "with a struct" do
-      Spectator::Mock.inject(MockedStruct, :mock_name, method1: 123) do
+      struct MockedStruct
+        getter method1 = 42
+
+        def method2
+          :original
+        end
+
+        def method3
+          "original"
+        end
+
+        def instance_variables
+          [{{@type.instance_vars.map(&.name.symbolize).splat}}]
+        end
+      end
+
+      Spectator::Mock.inject(:struct, MockedStruct, :mock_name, method1: 123) do
         stub def method2
           :stubbed
         end
diff --git a/src/spectator/mocks/mock.cr b/src/spectator/mocks/mock.cr
index f10d1c9..c472569 100644
--- a/src/spectator/mocks/mock.cr
+++ b/src/spectator/mocks/mock.cr
@@ -8,63 +8,56 @@ require "./value_stub"
 
 module Spectator
   module Mock
-    macro define_subclass(mocked_type, type_name, name = nil, **value_methods, &block)
-      {% if name %}@[::Spectator::StubbedName({{name}})]{% end %}
-      class {{type_name.id}} < {{mocked_type.id}}
-        include ::Spectator::Mocked
-
-        {% begin %}
-          private getter(_spectator_stubs) do
-            [
-              {% for key, value in value_methods %}
-                ::Spectator::ValueStub.new({{key.id.symbolize}}, {{value}}),
-              {% end %}
-            ] of ::Spectator::Stub
-          end
-        {% end %}
-
-        def _spectator_clear_stubs : Nil
-          @_spectator_stubs = nil
-        end
-
-        # Returns the mock's name formatted for user output.
-        private def _spectator_stubbed_name : String
-          \{% if anno = @type.annotation(::Spectator::StubbedName) %}
-            "#<Mock {{mocked_type.id}} \"" + \{{(anno[0] || :Anonymous.id).stringify}} + "\">"
-          \{% else %}
-            "#<Mock {{mocked_type.id}}>"
-          \{% end %}
-        end
-
-        macro finished
-          stub_type {{mocked_type.id}}
-
-          {% if block %}{{block.body}}{% end %}
-        end
-      end
-    end
-
-    macro inject(type_name, name = nil, **value_methods, &block)
-      {% type = type_name.resolve
-         base = if type.class?
-                  :class
-                elsif type.struct?
-                  :struct
-                else
-                  raise "Unsupported mockable type - #{type}"
-                end.id %}
-
+    macro define_subtype(base, mocked_type, type_name, name = nil, **value_methods, &block)
       {% begin %}
         {% if name %}@[::Spectator::StubbedName({{name}})]{% end %}
-        {{base}} ::{{type.name}}
+        {{base.id}} {{type_name.id}} < {{mocked_type.id}}
           include ::Spectator::Mocked
 
-          {% if type.class? %}
+          {% begin %}
+            private getter(_spectator_stubs) do
+              [
+                {% for key, value in value_methods %}
+                  ::Spectator::ValueStub.new({{key.id.symbolize}}, {{value}}),
+                {% end %}
+              ] of ::Spectator::Stub
+            end
+          {% end %}
+
+          def _spectator_clear_stubs : Nil
+            @_spectator_stubs = nil
+          end
+
+          # Returns the mock's name formatted for user output.
+          private def _spectator_stubbed_name : String
+            \{% if anno = @type.annotation(::Spectator::StubbedName) %}
+              "#<Mock {{mocked_type.id}} \"" + \{{(anno[0] || :Anonymous.id).stringify}} + "\">"
+            \{% else %}
+              "#<Mock {{mocked_type.id}}>"
+            \{% end %}
+          end
+
+          macro finished
+            stub_type {{mocked_type.id}}
+
+            {% if block %}{{block.body}}{% end %}
+          end
+        end
+      {% end %}
+    end
+
+    macro inject(base, type_name, name = nil, **value_methods, &block)
+      {% begin %}
+        {% if name %}@[::Spectator::StubbedName({{name}})]{% end %}
+        {{base.id}} {{type_name.id}}
+          include ::Spectator::Mocked
+
+          {% if base == :class %}
             @@_spectator_mock_registry = ::Spectator::ReferenceMockRegistry.new
-          {% elsif type.struct? %}
+          {% elsif base == :struct %}
             @@_spectator_mock_registry = ::Spectator::ValueMockRegistry(self).new
           {% else %}
-            {% raise "Unsupported type for injecting mock" %}
+            {% raise "Unsupported base type #{base} for injecting mock" %}
           {% end %}
 
           private def _spectator_stubs
@@ -86,14 +79,14 @@ module Spectator
           # Returns the mock's name formatted for user output.
           private def _spectator_stubbed_name : String
             \{% if anno = @type.annotation(::Spectator::StubbedName) %}
-              "#<Mock {{type.name}} \"" + \{{(anno[0] || :Anonymous.id).stringify}} + "\">"
+              "#<Mock {{type_name.id}} \"" + \{{(anno[0] || :Anonymous.id).stringify}} + "\">"
             \{% else %}
-              "#<Mock {{type.name}}>"
+              "#<Mock {{type_name.id}}>"
             \{% end %}
           end
 
           macro finished
-            stub_type {{type.name}}
+            stub_type {{type_name.id}}
 
             {% if block %}{{block.body}}{% end %}
           end