diff --git a/changelog.d/17864.misc b/changelog.d/17864.misc
new file mode 100644
index 0000000000..3402bc2582
--- /dev/null
+++ b/changelog.d/17864.misc
@@ -0,0 +1 @@
+Prevent exception from receiving an invalid `Content-Type` response header upon fetching remote media.
\ No newline at end of file
diff --git a/synapse/media/media_repository.py b/synapse/media/media_repository.py
index 859b30e029..22ae545acd 100644
--- a/synapse/media/media_repository.py
+++ b/synapse/media/media_repository.py
@@ -961,7 +961,11 @@ class MediaRepository:
                 )
                 raise SynapseError(502, "Failed to fetch remote media")
 
-            if b"Content-Type" in headers:
+            if (
+                b"Content-Type" in headers
+                and len(headers[b"Content-Type"]) > 0
+                and headers[b"Content-Type"][0] is not None
+            ):
                 media_type = headers[b"Content-Type"][0].decode("ascii")
             else:
                 media_type = "application/octet-stream"