diff --git a/mercurial/cext/revlog.c b/mercurial/cext/revlog.c
--- a/mercurial/cext/revlog.c
+++ b/mercurial/cext/revlog.c
@@ -87,9 +87,9 @@
 static Py_ssize_t inline_scan(indexObject *self, const char **offsets);
 
 #if LONG_MAX == 0x7fffffffL
-static char *tuple_format = "Kiiiiiis#";
+static char *index_entry_format = "Kiiiiiis#";
 #else
-static char *tuple_format = "kiiiiiis#";
+static char *index_entry_format = "kiiiiiis#";
 #endif
 
 /* A RevlogNG v1 index entry is 64 bytes long. */
@@ -209,7 +209,7 @@
 	parent_2 = getbe32(data + 28);
 	c_node_id = data + 32;
 
-	entry = Py_BuildValue(tuple_format, offset_flags, comp_len,
+	entry = Py_BuildValue(index_entry_format, offset_flags, comp_len,
 			      uncomp_len, base_rev, link_rev,
 			      parent_1, parent_2, c_node_id, 20);