diff --git a/biggraphite/drivers/cassandra.py b/biggraphite/drivers/cassandra.py
index 6dc65b4ed7..e3cf69c155 100755
--- a/biggraphite/drivers/cassandra.py
+++ b/biggraphite/drivers/cassandra.py
@@ -936,8 +936,8 @@ def _extract_results(query_results):
                     n_metrics += 1
                     if n_metrics > self.max_metrics_per_pattern:
                         raise TooManyMetrics(
-                            "Query yields more than %d results" %
-                            (self.max_metrics_per_pattern)
+                            "Query %s on %s yields more than %d results" %
+                            (glob, table, self.max_metrics_per_pattern)
                         )
                     yield result[0]
 
diff --git a/tests/test_cassandra.py b/tests/test_cassandra.py
index 8ff71220d7..6f4ac7f717 100644
--- a/tests/test_cassandra.py
+++ b/tests/test_cassandra.py
@@ -288,6 +288,17 @@ def assert_find(glob, expected_matches):
         self.accessor.drop_all_metrics()
         assert_find("*", [])
 
+    def test_glob_too_many_directories(self):
+        for name in "a", "a.b", "x.y.z":
+            metric = bg_test_utils.make_metric(name)
+            self.accessor.create_metric(metric)
+
+        old_value = self.accessor.max_metrics_per_pattern
+        self.accessor.max_metrics_per_pattern = 1
+        with self.assertRaises(bg_cassandra.TooManyMetrics):
+            list(self.accessor.glob_directory_names('**'))
+        self.accessor.max_metrics_per_pattern = old_value
+
     def test_create_metrics(self):
         meta_dict = {
             "aggregator": bg_accessor.Aggregator.last,