diff --git a/testing/tools/fixup_pdf_template.py b/testing/tools/fixup_pdf_template.py
index da2d608..1d38117 100755
--- a/testing/tools/fixup_pdf_template.py
+++ b/testing/tools/fixup_pdf_template.py
@@ -182,7 +182,7 @@
           if override_line_endings:
             # Replace CRLF with LF line endings for .in files.
             if line.endswith(WINDOWS_LINE_ENDING):
-              line = line.removesuffix(WINDOWS_LINE_ENDING) + UNIX_LINE_ENDING
+              line = line[:-len(WINDOWS_LINE_ENDING)] + UNIX_LINE_ENDING
               end_of_file_line_ending = True
             else:
               end_of_file_line_ending = line.endswith(UNIX_LINE_ENDING)