diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 5f24822..5b31b61 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -114,25 +114,44 @@
 #define MBEDTLS_ERR_ERROR_GENERIC_ERROR       -0x0001  /**< Generic error */
 #define MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED -0x006E  /**< This is a bug in the library */
 
-
-#if defined(MBEDTLS_TEST_HOOKS) && defined(MBEDTLS_ERROR_C)
 /**
- * \brief Set a function pointer (hook) to allow for invasive testing of error
- *        code addition.
+ * \brief Combines a high-level and low-level error code together.
  *
- * This hook is used in the test infrastructure to report on errors when
- * combining two error codes of the same level.
- *
- * \param hook    hook to invasive testing function
+ *        Wrapper function for mbedtls_err_add_ext(). See that function for
+ *        more details.
  */
-void mbedtls_set_err_add_hook( void (*hook)( int, int, const char *, int ) );
-int mbedtls_err_add( int high, int low, const char *file, int line );
-#define MBEDTLS_ERR_ADD( high, low )  \
-    ( mbedtls_err_add( high, low, __FILE__, __LINE__ ) )
-#else
-#define MBEDTLS_ERR_ADD( high, low ) \
-    ( ( high ) + ( low ) )
-#endif /* MBEDTLS_TEST_HOOKS */
+#define mbedtls_error_add( high, low ) \
+        mbedtls_error_add_ext( high, low, __FILE__, __LINE__ )
+
+/**
+ * \brief Testing hook called before adding/combining two error codes together.
+ *        Only used when invasive testing is enabled via MBEDTLS_TEST_HOOKS.
+ */
+void (*mbedtls_test_hook_error_add)( int, int, const char *, int );
+
+/**
+ * \brief Combines a high-level and low-level error code together.
+ *
+ *        This function can be called directly however it is usually
+ *        called via the mbedtls_error_add macro.
+ *
+ * \note  When invasive testing is enabled via MBEDTLS_TEST_HOOKS also try to
+ *        call mbedtls_test_hook_error_add.
+ *
+ * \param high      high-level error code. See error.h for more details.
+ * \param low       low-level error code. See error.h for more details.
+ * \param file      file where this error code addition occured.
+ * \param line      line where this error code addition occured.
+ */
+static inline int mbedtls_error_add_ext( int high, int low,
+                                     const char *file, int line )
+{
+#if defined(MBEDTLS_TEST_HOOKS)
+    if( *mbedtls_test_hook_error_add != NULL )
+        ( *mbedtls_test_hook_error_add )( high, low, file, line );
+#endif
+    return( high + low );
+}
 
 /**
  * \brief Translate a mbed TLS error code into a string representation,