diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index cd7731e..d164e9f 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -114,6 +114,16 @@
 #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)
+void (*mbedtls_test_err_add_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
+
 /**
  * \brief Translate a mbed TLS error code into a string representation,
  *        Result is truncated if necessary and always includes a terminating