diff --git a/.gitignore b/.gitignore
index 7a928b4..b6d1948 100644
--- a/.gitignore
+++ b/.gitignore
@@ -65,4 +65,8 @@ target/
 #Ipython Notebook
 .ipynb_checkpoints
 
-**/noise.prof
\ No newline at end of file
+**/noise.prof
+
+# IDE Stuff
+.idea/
+.vscode/
\ No newline at end of file
diff --git a/sox/transform.py b/sox/transform.py
index 83e0506..f067f45 100644
--- a/sox/transform.py
+++ b/sox/transform.py
@@ -836,6 +836,9 @@ def build_array(self,
             'append_comments': True,
         }
 
+        if self.output_format.get('file_type') is not None:
+            output_format['file_type'] = self.output_format['file_type']
+
         if self.output_format.get('rate') is not None:
             output_format['rate'] = self.output_format['rate']
 
diff --git a/tests/test_transform.py b/tests/test_transform.py
index 14a99f8..5bef3dd 100644
--- a/tests/test_transform.py
+++ b/tests/test_transform.py
@@ -1,6 +1,7 @@
 from pathlib import Path
 import os
 import unittest
+from unittest.mock import patch
 
 from sox import transform, file_info
 from sox.core import SoxError
@@ -676,6 +677,7 @@ def test_append_comments_invalid(self):
         with self.assertRaises(ValueError):
             self.tfm._output_format_args({'append_comments': None})
 
+
 class TestTransformerBuild(unittest.TestCase):
     def setUp(self):
         self.tfm = new_transformer()
@@ -814,6 +816,17 @@ def test_bits_invalid(self):
         with self.assertRaises(ValueError):
             self.tfm.build_array(INPUT_FILE)
 
+    def test_output_file_type(self):
+        with patch("sox.transform.sox") as patched_sox_call:
+            patched_sox_call.return_value = 0, b"", b""
+            self.tfm.build_array(INPUT_FILE)
+            sox_cmd_args, src_array, decode_out_with_utf = patched_sox_call.call_args[0]
+            self.assertIn("raw", sox_cmd_args)  # default output file type
+            self.tfm.set_output_format(file_type="gsm")
+            self.tfm.build_array(INPUT_FILE)
+            sox_cmd_args, src_array, decode_out_with_utf = patched_sox_call.call_args[0]
+            self.assertIn("gsm", sox_cmd_args)  # desired output file type
+
 
 class TestTransformerClearEffects(unittest.TestCase):