diff --git a/posix/except.cpp b/posix/except.cpp
index a45694b1..4feae9f2 100644
--- a/posix/except.cpp
+++ b/posix/except.cpp
@@ -11,7 +11,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2010, 2017,
+ * Copyright 2010-2018
  *     Danny Robson <danny@nerdcruft.net>
  */
 
@@ -98,6 +98,16 @@ error::throw_code (int code)
 }
 
 
+///////////////////////////////////////////////////////////////////////////////
+const char*
+error::what (void) const noexcept
+{
+    return strerror (m_code);
+}
+
+
+
+
 ///////////////////////////////////////////////////////////////////////////////
 using util::posix::eai;
 
diff --git a/posix/except.hpp b/posix/except.hpp
index f3b03db6..fb75d913 100644
--- a/posix/except.hpp
+++ b/posix/except.hpp
@@ -11,7 +11,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2010, 2017,
+ * Copyright 2010-2018
  *     Danny Robson <danny@nerdcruft.net>
  */
 
@@ -39,6 +39,8 @@ namespace util::posix {
         static void throw_code [[gnu::noreturn]] (void);
         static void throw_code [[gnu::noreturn]] (int code);
 
+        virtual const char* what (void) const noexcept final override;
+
         template <typename T>
         static T try_value (T value)
         {
@@ -48,7 +50,7 @@ namespace util::posix {
         }
 
     private:
-        int m_code;
+        int const m_code;
     };