diff --git a/src/Oci8/Schema/Grammars/OracleGrammar.php b/src/Oci8/Schema/Grammars/OracleGrammar.php
index ffd1eae8..c9c69057 100644
--- a/src/Oci8/Schema/Grammars/OracleGrammar.php
+++ b/src/Oci8/Schema/Grammars/OracleGrammar.php
@@ -377,7 +377,7 @@ public function compileDrop(Blueprint $blueprint, Fluent $command)
     public function compileDropAllTables()
     {
         return 'BEGIN
-            FOR c IN (SELECT table_name FROM user_tables) LOOP
+            FOR c IN (SELECT table_name FROM user_tables WHERE secondary = \'N\') LOOP
             EXECUTE IMMEDIATE (\'DROP TABLE "\' || c.table_name || \'" CASCADE CONSTRAINTS\');
             END LOOP;