diff --git a/ChangeLog.d/error-unification.txt b/ChangeLog.d/error-unification.txt
new file mode 100644
index 000000000..e1790d29d
--- /dev/null
+++ b/ChangeLog.d/error-unification.txt
@@ -0,0 +1,7 @@
+API changes
+   * The PSA and Mbed TLS error space are now unified. This means that
+     mbedtls_xxx() functions can return PSA_ERROR_xxx values.
+     There is no longer a distinction between "low-level" and "high-level"
+     Mbed TLS error codes..
+     This will not affect most applications since in both cases, the
+     error values are between -32767 and -1 as before.