diff --git a/README.md b/README.md
index b4bd9c5..6dee0d1 100644
--- a/README.md
+++ b/README.md
@@ -148,6 +148,8 @@ namespace some_namespace
 ENUM_HPP_REGISTER_TRAITS(color)
 
 int main() {
+    using color = some_namespace::color;
+
     // to string
     static_assert(enum_hpp::to_string(color::red) == "red");
 
@@ -158,6 +160,34 @@ int main() {
 }
 ```
 
+### Adapting external enums
+
+```cpp
+namespace external_ns
+{
+    enum class external_enum : unsigned short {
+        a = 10,
+        b,
+        c = a + b
+    };
+
+    // should be in the same namespace
+    ENUM_HPP_TRAITS_DECL(external_enum,
+        (a)
+        (b)
+        (c))
+}
+
+ENUM_HPP_REGISTER_TRAITS(external_ns::external_enum)
+
+int main() {
+    using ee = external_ns::external_enum;
+    static_assert(enum_hpp::to_string(ee::a) == "a");
+    static_assert(enum_hpp::from_string<ee>("c") == ee::c);
+    return 0;
+}
+```
+
 ## API
 
 ### Enum traits
@@ -170,11 +200,16 @@ ENUM_HPP_DECL(
     /*fields*/)
 
 // declare enum class
-ENUM_HPP_DECL(
+ENUM_HPP_CLASS_DECL(
     /*enum_name*/,
     /*underlying_type*/,
     /*fields*/)
 
+// declare only traits
+ENUM_HPP_TRAITS_DECL(
+    /*enum_name*/,
+    /*fields*/)
+
 struct /*enum_name*/_traits {
     using underlying_type = /*underlying_type*/;
     static constexpr std::size_t size = /*field_count*/;
diff --git a/untests/enum_tests.cpp b/untests/enum_tests.cpp
index b54edd5..bd67a75 100644
--- a/untests/enum_tests.cpp
+++ b/untests/enum_tests.cpp
@@ -53,10 +53,25 @@ namespace some_namespace
         (_181)(_182)(_183)(_184)(_185)(_186)(_187)(_188)(_189)(_190)(_191)(_192)(_193)(_194)(_195)(_196)(_197)(_198)(_199)(_200)
         (_201)(_202)(_203)(_204)(_205)(_206)(_207)(_208)(_209)(_210)(_211)(_212)(_213)(_214)(_215)(_216)(_217)(_218)(_219)(_220)
         (_221)(_222)(_223)(_224)(_225)(_226)(_227)(_228)(_229)(_230)(_231)(_232)(_233)(_234)(_235)(_236)(_237)(_238)(_239)(_240))
+
+    namespace exns
+    {
+        enum class external_enum : unsigned short {
+            a = 10,
+            b,
+            c = a + b
+        };
+
+        ENUM_HPP_TRAITS_DECL(external_enum,
+            (a)
+            (b)
+            (c))
+    }
 }
 
 ENUM_HPP_REGISTER_TRAITS(some_namespace::color)
 ENUM_HPP_REGISTER_TRAITS(some_namespace::numbers)
+ENUM_HPP_REGISTER_TRAITS(some_namespace::exns::external_enum)
 
 TEST_CASE("enum") {
     namespace sn = some_namespace;
@@ -375,3 +390,18 @@ TEST_CASE("enum") {
         }
     }
 }
+
+TEST_CASE("external_enum") {
+    using ee = some_namespace::exns::external_enum;
+    STATIC_REQUIRE(std::is_same_v<enum_hpp::underlying_type<ee>, unsigned short>);
+    STATIC_REQUIRE(enum_hpp::size<ee>() == 3);
+
+    STATIC_REQUIRE(enum_hpp::names<ee>()[0] == "a");
+    STATIC_REQUIRE(enum_hpp::names<ee>()[2] == "c");
+
+    STATIC_REQUIRE(enum_hpp::values<ee>()[0] == ee::a);
+    STATIC_REQUIRE(enum_hpp::values<ee>()[2] == ee::c);
+
+    STATIC_REQUIRE(enum_hpp::to_string(ee::c) == "c");
+    STATIC_REQUIRE(enum_hpp::from_string<ee>("b") == ee::b);
+}