diff --git a/git_refs.py b/git_refs.py
index 3c8a9867..2d4a8090 100644
--- a/git_refs.py
+++ b/git_refs.py
@@ -131,11 +131,14 @@ class GitRefs(object):
     base = os.path.join(self._gitdir, prefix)
     for name in platform_utils.listdir(base):
       p = os.path.join(base, name)
-      if platform_utils.isdir(p):
+      # We don't implement the full ref validation algorithm, just the simple
+      # rules that would show up in local filesystems.
+      # https://git-scm.com/docs/git-check-ref-format
+      if name.startswith('.') or name.endswith('.lock'):
+        pass
+      elif platform_utils.isdir(p):
         self._mtime[prefix] = os.path.getmtime(base)
         self._ReadLoose(prefix + name + '/')
-      elif name.endswith('.lock'):
-        pass
       else:
         self._ReadLoose1(p, prefix + name)
 
@@ -144,7 +147,7 @@ class GitRefs(object):
       with open(path) as fd:
         mtime = os.path.getmtime(path)
         ref_id = fd.readline()
-    except (IOError, OSError):
+    except (OSError, UnicodeError):
       return
 
     try: