diff --git a/scripts/osv/trace.py b/scripts/osv/trace.py
index d16c9a3cc43344f90b1acd9e5da2bb7f548c6049..2d11f66ab9d81ed4597a43920ed3a4b805d33b7c 100644
--- a/scripts/osv/trace.py
+++ b/scripts/osv/trace.py
@@ -162,7 +162,7 @@ def split_format(format_str):
             fmt = str(c)
             while c.isdigit():
                 c = next(chars)
-                fmt += c
+                fmt += str(c)
             yield fmt
 
 formatters = {