diff --git a/Charon/filetypes/OpenPackagingConvention.py b/Charon/filetypes/OpenPackagingConvention.py
index f5d8e6f..ab33d8b 100644
--- a/Charon/filetypes/OpenPackagingConvention.py
+++ b/Charon/filetypes/OpenPackagingConvention.py
@@ -47,7 +47,7 @@ def openStream(self, stream: IO[bytes], mime: str = "application/x-opc",
                    mode: OpenMode = OpenMode.ReadOnly) -> None:
         self._mode = mode
         self._stream = stream  # A copy in case we need to rewind for toByteArray. We should mostly be reading via self._zipfile.
-        self._zipfile = zipfile.ZipFile(self._stream, self._mode.value, compression=zipfile.ZIP_DEFLATED)
+        self._zipfile = zipfile.ZipFile(self._stream, self._mode.value, compression=zipfile.ZIP_DEFLATED, allowZip64=True)
 
         self._readContentTypes()  # Load or create the content types element.
         self._readRels()  # Load or create the relations.
@@ -211,7 +211,7 @@ def toByteArray(self, offset: int = 0, count: int = -1) -> bytes:
         self._stream.seek(offset)
         result = self._stream.read(count)
 
-        self._zipfile = zipfile.ZipFile(self._stream, self._mode.value, compression=zipfile.ZIP_DEFLATED)
+        self._zipfile = zipfile.ZipFile(self._stream, self._mode.value, compression=zipfile.ZIP_DEFLATED, allowZip64=True)
         return result
 
     ##  Adds a new content type to the archive.
@@ -350,8 +350,10 @@ def _resizeImage(self, virtual_path: str, width: int, height: int) -> IO[bytes]:
     def _readRels(self) -> None:
         assert self._zipfile is not None
 
-        self._relations[""] = ET.Element("Relationships",
-                                         xmlns="http://schemas.openxmlformats.org/package/2006/relationships")  # There must always be a global relationships document.
+        self._relations[""] = ET.Element(
+            "Relationships",
+            xmlns="http://schemas.openxmlformats.org/package/2006/relationships"
+        )  # There must always be a global relationships document.
 
         # Below is some parsing of paths and extensions.
         # Normally you'd use os.path for this. But this is platform-dependent.
@@ -412,8 +414,10 @@ def _readContentTypes(self) -> None:
             if content_types_element:
                 self._content_types_element = content_types_element
         if not self._content_types_element:
-            self._content_types_element = ET.Element("Types",
-                                                     xmlns="http://schemas.openxmlformats.org/package/2006/content-types")
+            self._content_types_element = ET.Element(
+                "Types",
+                xmlns="http://schemas.openxmlformats.org/package/2006/content-types"
+            )
         # If there is no type for the .rels file, create it.
         if self._mode != OpenMode.ReadOnly:
             for type_element in self._content_types_element.iterfind(