diff --git a/docling/backend/mspowerpoint_backend.py b/docling/backend/mspowerpoint_backend.py
index 9aaf41f5..66311de9 100644
--- a/docling/backend/mspowerpoint_backend.py
+++ b/docling/backend/mspowerpoint_backend.py
@@ -46,6 +46,10 @@ class MsPowerpointDocumentBackend(DeclarativeDocumentBackend, PaginatedDocumentB
 
         self.pptx_obj = None
         self.valid = False
+        self.xpath_expr = etree.XPath(".//a:blip", namespaces={
+            "a": "http://schemas.openxmlformats.org/drawingml/2006/main",
+            "r": "http://schemas.openxmlformats.org/officeDocument/2006/relationships",
+        })
         try:
             if isinstance(self.path_or_stream, BytesIO):
                 self.pptx_obj = Presentation(self.path_or_stream)