diff --git a/ext/oci8/oci8.c b/ext/oci8/oci8.c
index 18ec63eb5fd..2d25803f75a 100644
--- a/ext/oci8/oci8.c
+++ b/ext/oci8/oci8.c
@@ -376,10 +376,16 @@ PHP_MINIT_FUNCTION(oci)
 	REGISTER_LONG_CONSTANT("OCI_D_LOB",OCI_DTYPE_LOB, CONST_CS | CONST_PERSISTENT);
 	REGISTER_LONG_CONSTANT("OCI_D_ROWID",OCI_DTYPE_ROWID, CONST_CS | CONST_PERSISTENT);
 
+#ifdef ZTS 
+	#define PHP_OCI_INIT_MODE OCI_THREADED
+#else
+	#define PHP_OCI_INIT_MODE OCI_DEFAULT
+#endif
+
 #if OCI_USE_EMALLOC
-    OCIInitialize(OCI_DEFAULT, NULL, ocimalloc, ocirealloc, ocifree);
+    OCIInitialize(PHP_OCI_INIT_MODE, NULL, ocimalloc, ocirealloc, ocifree);
 #else
-    OCIInitialize(OCI_DEFAULT, NULL, NULL, NULL, NULL);
+    OCIInitialize(PHP_OCI_INIT_MODE, NULL, NULL, NULL, NULL);
 #endif
 
 	return SUCCESS;