diff --git a/src/config/config.cc b/src/config/config.cc
index 268ef116..39346cd5 100644
--- a/src/config/config.cc
+++ b/src/config/config.cc
@@ -51,6 +51,36 @@ std::string to_string(const diagram_type t)
     }
 }
 
+void plantuml::append(const plantuml &r)
+{
+    before.insert(before.end(), r.before.begin(), r.before.end());
+    after.insert(after.end(), r.after.begin(), r.after.end());
+}
+
+void inheritable_diagram_options::inherit(
+    const inheritable_diagram_options &parent)
+{
+    if (!glob.has_value && parent.glob.has_value)
+        glob.append(parent.glob());
+
+    if (!using_namespace.has_value && parent.using_namespace.has_value)
+        using_namespace.append(parent.using_namespace());
+
+    if (!include_relations_also_as_members.has_value &&
+        parent.include_relations_also_as_members.has_value)
+        include_relations_also_as_members.append(
+            parent.include_relations_also_as_members());
+
+    if (!include.has_value && parent.include.has_value)
+        include.append(parent.include());
+
+    if (!exclude.has_value && parent.exclude.has_value)
+        exclude.append(parent.exclude());
+
+    if (!puml.has_value && parent.puml.has_value)
+        puml.append(parent.puml());
+}
+
 bool diagram::should_include_entities(const std::string &ent)
 {
     for (const auto &ex : exclude().entity_types) {
diff --git a/src/config/config.h b/src/config/config.h
index 0df947c2..42acb1d5 100644
--- a/src/config/config.h
+++ b/src/config/config.h
@@ -38,11 +38,7 @@ struct plantuml {
     std::vector<std::string> before;
     std::vector<std::string> after;
 
-    void append(const plantuml &r)
-    {
-        before.insert(before.end(), r.before.begin(), r.before.end());
-        after.insert(after.end(), r.after.begin(), r.after.end());
-    }
+    void append(const plantuml &r);
 };
 
 struct filter {
@@ -70,14 +66,12 @@ enum class diagram_type { class_diagram, sequence_diagram, package_diagram };
 std::string to_string(const diagram_type t);
 
 template <typename T> void append_value(T &l, const T &r) { l = r; }
-// template<> void append_value<bool>(bool &l, const bool&r) {l = r;}
 
 template <typename T> struct option {
     option(const std::string &name_)
         : name{name_}
     {
     }
-
     option(const std::string &name_, const T &initial_value)
         : name{name_}
         , value{initial_value}
@@ -85,11 +79,6 @@ template <typename T> struct option {
     {
     }
 
-    std::string name;
-
-    T value;
-    bool has_value{false};
-
     void append(const T &r)
     {
         append_value(value, r);
@@ -106,6 +95,10 @@ template <typename T> struct option {
     T &operator()() { return value; }
 
     const T &operator()() const { return value; }
+
+    std::string name;
+    T value;
+    bool has_value{false};
 };
 
 struct inheritable_diagram_options {
@@ -117,28 +110,7 @@ struct inheritable_diagram_options {
     option<filter> exclude{"exclude"};
     option<plantuml> puml{"plantuml"};
 
-    void inherit(const inheritable_diagram_options &parent)
-    {
-        if (!glob.has_value && parent.glob.has_value)
-            glob.append(parent.glob());
-
-        if (!using_namespace.has_value && parent.using_namespace.has_value)
-            using_namespace.append(parent.using_namespace());
-
-        if (!include_relations_also_as_members.has_value &&
-            parent.include_relations_also_as_members.has_value)
-            include_relations_also_as_members.append(
-                parent.include_relations_also_as_members());
-
-        if (!include.has_value && parent.include.has_value)
-            include.append(parent.include());
-
-        if (!exclude.has_value && parent.exclude.has_value)
-            exclude.append(parent.exclude());
-
-        if (!puml.has_value && parent.puml.has_value)
-            puml.append(parent.puml());
-    }
+    void inherit(const inheritable_diagram_options &parent);
 };
 
 struct diagram : public inheritable_diagram_options {