diff --git a/src/components/dependency_injection/spec/compiler_passes/process_parameters_spec.cr b/src/components/dependency_injection/spec/compiler_passes/process_parameters_spec.cr
index 0a5909e0..3394f20e 100644
--- a/src/components/dependency_injection/spec/compiler_passes/process_parameters_spec.cr
+++ b/src/components/dependency_injection/spec/compiler_passes/process_parameters_spec.cr
@@ -63,4 +63,40 @@ describe ADI::ServiceContainer::ProcessParameters, tags: "compiled" do
       end
     CR
   end
+
+  it "does not override value of manually wired up parameters with default value" do
+    ASPEC::Methods.assert_success <<-CR, codegen: true
+      require "../spec_helper.cr"
+
+      class SomeService
+        def initialize(@id : Int32 = 123); end
+      end
+
+      module MyExtension
+        macro included
+          macro finished
+            {% verbatim do %}
+              {%
+                SERVICE_HASH["some_service"] = {
+                  class: SomeService,
+                  parameters: {
+                    id: {value: 999}
+                  }
+                }
+              %}
+            {% end %}
+          end
+        end
+      end
+
+      ADI.add_compiler_pass MyExtension, :before_optimization, 1028
+      ADI::ServiceContainer.new
+
+      macro finished
+        macro finished
+          it { \\{{ADI::ServiceContainer::SERVICE_HASH["some_service"]["parameters"]["id"]["value"].stringify}}.should eq "999" }
+        end
+      end
+    CR
+  end
 end
diff --git a/src/components/dependency_injection/src/compiler_passes/process_parameters.cr b/src/components/dependency_injection/src/compiler_passes/process_parameters.cr
index e6be8f71..8915abc1 100644
--- a/src/components/dependency_injection/src/compiler_passes/process_parameters.cr
+++ b/src/components/dependency_injection/src/compiler_passes/process_parameters.cr
@@ -36,7 +36,7 @@ module Athena::DependencyInjection::ServiceContainer::ProcessParameters
 
               # Set the default value is there is one.
               if !(dv = initializer_arg.default_value).is_a?(Nop)
-                default_value = value = dv
+                default_value = dv
               end
 
               parameters[initializer_arg.name.id.stringify] = {
@@ -47,7 +47,7 @@ module Athena::DependencyInjection::ServiceContainer::ProcessParameters
                 restriction:          initializer_arg.restriction,
                 resolved_restriction: ((r = initializer_arg.restriction).is_a?(Nop) ? nil : r.resolve),
                 default_value:        default_value,
-                value:                value || default_value,
+                value:                value.nil? ? default_value : value,
               }
             end
           end