diff --git a/sql/patch_69_70_b.sql b/sql/patch_69_70_b.sql
index 75c168341b89f08b6833f8743d80fe696526cc98..e01b730c9c46bfcf69e49188c3eb4869fa04cd5e 100644
--- a/sql/patch_69_70_b.sql
+++ b/sql/patch_69_70_b.sql
@@ -12,9 +12,9 @@
 ALTER TABLE mapping_set DROP COLUMN schema_build;
 ALTER TABLE mapping_set ADD COLUMN (internal_schema_build VARCHAR(20) NOT NULL);
 ALTER TABLE mapping_set ADD COLUMN (external_schema_build VARCHAR(20) NOT NULL);
+TRUNCATE TABLE mapping_set;
 ALTER TABLE mapping_set ADD UNIQUE KEY mapping_idx (internal_schema_build, external_schema_build);
 TRUNCATE TABLE seq_region_mapping;
-TRUNCATE TABLE mapping_set;
 
 
 # Patch identifier