diff --git a/abi/vfabia64/vfabia64.rst b/abi/vfabia64/vfabia64.rst
index 302ee640..aecd7b29 100644
--- a/abi/vfabia64/vfabia64.rst
+++ b/abi/vfabia64/vfabia64.rst
@@ -1489,6 +1489,13 @@ Masked signature generation for ``[not]inbranch`` clause.
 |``#pragma omp declare simd notinbranch`` |No     |Yes     |Yes   |No      |
 +-----------------------------------------+-------+--------+------+--------+
 
+Inactive lanes
+--------------
+
+In a masked vector function, the contents of the inactive lanes of the
+input parameters and the inactive lanes of the return value are
+undefined.
+
 Advanced SIMD masking
 ---------------------