diff --git a/pdftext/pdf/chars.py b/pdftext/pdf/chars.py
index 98e8d20..605e036 100644
--- a/pdftext/pdf/chars.py
+++ b/pdftext/pdf/chars.py
@@ -34,7 +34,7 @@ def get_pdfium_chars(pdf, page_range, flatten_pdf, fontname_sample_freq=settings
 
         if flatten_pdf:
             # Flatten form fields and annotations into page contents.
-            flatten(pdf, page)
+            flatten(page)
 
             # Flattening invalidates existing handles to the page.
             # It is necessary to re-initialize the page handle after flattening.
diff --git a/pyproject.toml b/pyproject.toml
index 39a5240..2c87a84 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "pdftext"
-version = "0.3.12"
+version = "0.3.13"
 description = "Extract structured text from pdfs quickly"
 authors = ["Vik Paruchuri <vik.paruchuri@gmail.com>"]
 license = "Apache-2.0"