diff --git a/pytools/persistent_dict.py b/pytools/persistent_dict.py
index 15732c367d8f24d55fe6f551ec7de653a7dc2e86..984dcfc1edeee3330f77d20dff8760f9506a4415 100644
--- a/pytools/persistent_dict.py
+++ b/pytools/persistent_dict.py
@@ -24,6 +24,10 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
 
+import logging
+logger = logging.getLogger(__name__)
+
+
 import sys
 import os
 
@@ -339,6 +343,8 @@ class PersistentDict(object):
 
                 if read_key != key:
                     # Key collision, oh well.
+                    logger.debug("key collsion in cache at '%s'"
+                            % self.container_dir)
                     raise NoSuchEntryError(key)
 
                 # {{{ load value