diff --git a/src/ocrmypdf/_pipeline.py b/src/ocrmypdf/_pipeline.py
index 08a6f51f..e5803f38 100644
--- a/src/ocrmypdf/_pipeline.py
+++ b/src/ocrmypdf/_pipeline.py
@@ -621,7 +621,7 @@ def select_ocr_image(
             # Calculate resolution based on the image size and page dimensions
             # without regard whatever resolution is in pageinfo (may differ or
             # be None)
-            bbox = textarea
+            bbox = [float(v) for v in textarea]
             xscale, yscale = float(xres) / 72.0, float(yres) / 72.0
             pixcoords = [bbox[0] * xscale,
                          im.height - bbox[3] * yscale,