diff --git a/src/backend/wopi/conversion/services.py b/src/backend/wopi/conversion/services.py
index 2597c725..c2c3dcaf 100644
--- a/src/backend/wopi/conversion/services.py
+++ b/src/backend/wopi/conversion/services.py
@@ -23,12 +23,15 @@ from wopi.conversion.source_url import build_source_url
 MIME_SNIFF_BYTES = 2048
 
 
-def _validate_conversion(item, user):
+def _validate_conversion(item, user, require_ready=True):
     """Run pre-flight checks and return the target extension and client options."""
     if item.type != models.ItemTypeChoices.FILE:
         raise ConversionRejected("Source item is not a file.")
 
-    if item.upload_state != models.ItemUploadStateChoices.READY:
+    ready_states = [models.ItemUploadStateChoices.READY]
+    if not require_ready:
+        ready_states.append(models.ItemUploadStateChoices.ANALYZING)
+    if item.upload_state not in ready_states:
         raise ConversionRejected("Source item is not ready.")
 
     if not item.get_abilities(user).get("update"):
@@ -95,7 +98,7 @@ def prepare_conversion(source_item, user):
     UI can display the converting state right away. The actual OnlyOffice
     conversion happens later in a celery task.
     """
-    target_extension, _ = _validate_conversion(source_item, user)
+    target_extension, _ = _validate_conversion(source_item, user, require_ready=False)
     parent = _resolve_destination_parent(source_item, user)
     target_filename = _target_filename(source_item, target_extension, parent, user)
 
diff --git a/src/backend/wopi/tests/conversion/test_services.py b/src/backend/wopi/tests/conversion/test_services.py
index 24af1497..353c6293 100644
--- a/src/backend/wopi/tests/conversion/test_services.py
+++ b/src/backend/wopi/tests/conversion/test_services.py
@@ -341,6 +341,33 @@ def test_prepare_conversion_returns_placeholder_in_converting_state(settings):
     assert placeholder.parent().id == parent.id
 
 
+def test_prepare_conversion_accepts_analyzing_source(settings):
+    """Queue a conversion while the source is still being analyzed."""
+    _configure_wopi(settings)
+    user = factories.UserFactory()
+    item = _file(user, update_upload_state=models.ItemUploadStateChoices.ANALYZING)
+
+    placeholder = services.prepare_conversion(item, user)
+
+    assert placeholder.upload_state == models.ItemUploadStateChoices.CONVERTING
+
+
+def test_perform_conversion_rejects_analyzing_source(settings):
+    """Never convert the bytes before analysis confirmed the source is safe."""
+    _configure_wopi(settings)
+    user = factories.UserFactory()
+    item = _file(user, update_upload_state=models.ItemUploadStateChoices.ANALYZING)
+    placeholder = factories.ItemFactory(
+        users=[(user, models.RoleChoices.EDITOR)],
+        type=models.ItemTypeChoices.FILE,
+        filename="document.docx",
+        update_upload_state=models.ItemUploadStateChoices.CONVERTING,
+    )
+
+    with pytest.raises(exceptions.ConversionRejected, match="not ready"):
+        services.perform_conversion(item, placeholder, user)
+
+
 def test_prepare_conversion_rejects_unsupported_extensions(settings):
     """Skip placeholder creation for files that cannot be converted."""
     _configure_wopi(settings)