diff --git a/mercurial/cext/revlog.c b/mercurial/cext/revlog.c
--- a/mercurial/cext/revlog.c
+++ b/mercurial/cext/revlog.c
@@ -157,7 +157,10 @@
 			                             sizeof(*self->offsets));
 			if (self->offsets == NULL)
 				return (const char *)PyErr_NoMemory();
-			inline_scan(self, self->offsets);
+			Py_ssize_t ret = inline_scan(self, self->offsets);
+			if (ret == -1) {
+				return NULL;
+			};
 		}
 		return self->offsets[pos];
 	}