diff --git a/doc/source/pre/whatsnew/1.3.rst b/doc/source/pre/whatsnew/1.3.rst
index 707608cb65e2d54c7854f01b0ded189c2ce2d815..f7dbd8fc0ef4373499d976fc3b908f04548e629e 100644
--- a/doc/source/pre/whatsnew/1.3.rst
+++ b/doc/source/pre/whatsnew/1.3.rst
@@ -219,3 +219,10 @@ image in the fundamental domain.
 
 This change is documented here for completeness.  We expect that the vast
 majority of users of Kwant will not be affected by it.
+
+ .. _whatsnew13-params-api-change:
+
+API change that affects low-level systems
+-----------------------------------------
+The `~kwant.system.System.hamiltonian` method of low-level systems must now accept a
+`params` keyword parameter.
diff --git a/doc/source/pre/whatsnew/1.4.rst b/doc/source/pre/whatsnew/1.4.rst
index 167b84301cdf6b0c95106aa8c02bf75bd96682f9..a06e5e55ad8b3c7693c5355cb552b093a012f608 100644
--- a/doc/source/pre/whatsnew/1.4.rst
+++ b/doc/source/pre/whatsnew/1.4.rst
@@ -343,3 +343,5 @@ Changes in Kwant 1.4.1
   adding the entry `Value functions may no longer take unnamed arguments`_.
 - Kwant no longer requires the existence of a `parameters` attribute for
   low-level systems.
+- A note about an :ref:`whatsnew13-params-api-change` that ocurred in Kwant
+  1.3 was added.