diff --git a/wcs_olap/feeder.py b/wcs_olap/feeder.py
index abf47ce..f87ee07 100644
--- a/wcs_olap/feeder.py
+++ b/wcs_olap/feeder.py
@@ -287,12 +287,12 @@ class WcsOlapFeeder(object):
         self.cur.execute("SELECT 1 FROM pg_type WHERE typname = 'jsonb'")
         return bool(self.cur.rowcount)
 
-    def hash_table_name(self, table_name):
+    def hash_table_name(self, table_name, hash_length=6):
         table_name = table_name.format(**self.default_ctx)
         if len(table_name) < 64:
             return table_name
         else:
-            return table_name[:57] + hashlib.md5(table_name).hexdigest()[:6]
+            return table_name[:63-hash_length] + hashlib.md5(table_name).hexdigest()[:hash_length]
 
     @property
     def default_ctx(self):
@@ -554,7 +554,8 @@ CREATE TABLE public.dates AS (SELECT
     def create_formdata_json_index(self, varname):
         if varname in self.formdata_json_index:
             return
-        index_name = self.hash_table_name('{formdata_table}_%s_json_idx' % varname)
+        index_name = self.hash_table_name('{formdata_table}_%s_json_idx' % varname,
+                hash_length=8)
         self.ex('CREATE INDEX {index_name} ON {generic_formdata_table} (("json_data"->>%s))',
                 ctx={'index_name': index_name}, vars=[varname])
         # prevent double creation