diff --git a/ZConfig/loader.py b/ZConfig/loader.py
index 2873317..27ca7df 100644
--- a/ZConfig/loader.py
+++ b/ZConfig/loader.py
@@ -28,6 +28,8 @@ import ZConfig.schema
 import ZConfig.url
 
 
+_schemesep = None
+
 def loadSchema(url):
     return SchemaLoader().loadURL(url)
 
@@ -131,11 +133,13 @@ class BaseLoader:
     def isPath(self, s):
         """Return True iff 's' should be handled as a filesystem path."""
         if ":" in s:
-            # XXX This assumes that one-character scheme identifiers
-            # are always Windows drive letters; I don't know of any
-            # one-character scheme identifiers.
-            scheme, rest = urllib.splittype(s)
-            return len(scheme) == 1
+            # XXX This assumes that scheme are always separated by "://"
+            # and that they do not contains any ':' or '/'
+            global _schemesep
+            if _schemesep is None:
+                import re
+                _schemesep = re.compile('^([^/:]+)://')
+            return _schemesep.match(s) is None
         else:
             return True
 
diff --git a/ZConfig/tests/test_loader.py b/ZConfig/tests/test_loader.py
index 0b7598d..6691b82 100644
--- a/ZConfig/tests/test_loader.py
+++ b/ZConfig/tests/test_loader.py
@@ -234,6 +234,9 @@ class LoaderTestCase(TestBase):
         assert_(not isPath("http://www.example.com/sample.conf"))
         assert_(not isPath("file:///etc/zope/zope.conf"))
         assert_(not isPath("file:///c|/foo/bar.conf"))
+        # protect directories containing ":"
+        assert_(isPath("/ab:c"))
+        assert_(isPath("ab:c"))
 
 
 class TestNonExistentResources(unittest.TestCase):