diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 8bb3f610ba..bfde49b4e4 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -1224,6 +1224,15 @@ class OPF:  # {{{
                 mt = item.get('media-type', '')
                 if mt and 'xml' not in mt and 'html' not in mt:
                     return item.get('href', None)
+        # OMF files have the cover as the first item in the spine
+        first_ref = self.first_spine_item()
+        if first_ref:
+            for item in self.itermanifest():
+                if item.get('href') == first_ref:
+                    mt = item.get('media-type', '')
+                    if mt and mt.lower() in {'image/jpeg', 'image/jpg', 'image/png', 'image/webp'}:
+                        return first_ref
+                    break
 
     @property
     def raster_cover(self):