diff --git a/rattail/pyramid/views/customergroups.py b/rattail/pyramid/views/customergroups.py
index af3a3bf6..fd7d5f79 100644
--- a/rattail/pyramid/views/customergroups.py
+++ b/rattail/pyramid/views/customergroups.py
@@ -29,7 +29,8 @@
 from edbob.pyramid.views import SearchableAlchemyGridView
 
 from rattail.pyramid.views import CrudView
-from rattail.db.model import CustomerGroup
+from rattail.pyramid import Session
+from rattail.db.model import CustomerGroup, CustomerGroupAssignment
 
 
 class CustomerGroupsGrid(SearchableAlchemyGridView):
@@ -84,6 +85,13 @@ class CustomerGroupCrud(CrudView):
                 ])
         return fs
 
+    def pre_delete(self, group):
+        # First remove customer associations.
+        q = Session.query(CustomerGroupAssignment)\
+            .filter(CustomerGroupAssignment.group == group)
+        for assignment in q:
+            Session.delete(assignment)
+
 
 def add_routes(config):
     config.add_route('customer_groups',         '/customer-groups')