--- a/tests/test-persistent-nodemap.t	Thu Jan 28 13:25:37 2021 +0100
+++ b/tests/test-persistent-nodemap.t	Thu Jan 28 13:15:34 2021 +0100
@@ -33,10 +33,18 @@
 
 #if rust
 
-Reported bug: some Rust code panics when handling the null revision
+Regression test for a previous bug in Rust/C FFI for the `Revlog_CAPI` capsule:
+in places where `mercurial/cext/revlog.c` function signatures use `Py_ssize_t`
+(64 bits on Linux x86_64), corresponding declarations in `rust/hg-cpython/src/cindex.rs`
+incorrectly used `libc::c_int` (32 bits).
+As a result, -1 passed from Rust for the null revision became 4294967295 in C.
 
-  $ hg log -r 00000000 2>&1 | grep panicked
-  thread '<unnamed>' panicked at 'called `Option::unwrap()` on a `None` value', hg-cpython/src/revlog.rs:* (glob)
+  $ hg log -r 00000000
+  changeset:   -1:000000000000
+  tag:         tip
+  user:        
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  
 
 #endif