diff --git a/src/utils/str.py b/src/utils/str.py
index 884938a62..a1dff4d5a 100644
--- a/src/utils/str.py
+++ b/src/utils/str.py
@@ -355,7 +355,7 @@ def timestamp(t):
         t = time.time()
     return time.ctime(t)
 
-_formatRe = re.compile('%(\.\d+f|[bfhiLnpqrstu%])')
+_formatRe = re.compile('%((?:\d+)?\.\d+f|[bfhiLnpqrstu%])')
 def format(s, *args, **kwargs):
     """w00t.