diff --git a/mps/manual/source/topic/error.rst b/mps/manual/source/topic/error.rst
index b584fcd7f5e..c0178a38d8d 100644
--- a/mps/manual/source/topic/error.rst
+++ b/mps/manual/source/topic/error.rst
@@ -235,6 +235,8 @@ this documentation.
 
 ``lockix.c: res == 0``
 
+``lockw3.c: lock->claims == 0``
+
     The client program has made a re-entrant call into the MPS. Look
     at the backtrace to see what it was. Common culprits are
     :term:`format methods` and :term:`stepper functions`.