Revise Changelog to clarify and add credit
diff --git a/ChangeLog b/ChangeLog
index 9f94210..defebd0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -34,8 +34,8 @@
    * Fixed the sample applications gen_key.c, cert_req.c and cert_write.c for
      builds where the configuration MBEDTLS_PEM_WRITE_C is not defined. Found
      by inestlerode. #559.
-   * Fixed default threading implementation to avoid accidental double
-     initialisations and double frees.
+   * Fixed pthread implementation to avoid unintended double initialisations
+     and double frees. (found by Niklas Amnebratt)
 
 Changes
    * Extended test coverage of special cases, and added new timing test suite.