diff --git a/src/ocrmypdf/exec/tesseract.py b/src/ocrmypdf/exec/tesseract.py
index ee6c9235..f61a6959 100644
--- a/src/ocrmypdf/exec/tesseract.py
+++ b/src/ocrmypdf/exec/tesseract.py
@@ -69,7 +69,8 @@ def has_textonly_pdf():
     """
     args_tess = [
         'tesseract',
-        '--print-parameters'
+        '--print-parameters',
+        'pdf'
     ]
     params = ''
     try: