diff --git a/server/src/lib.rs b/server/src/lib.rs
index 9c0cc9cb3..d1531d7e0 100644
--- a/server/src/lib.rs
+++ b/server/src/lib.rs
@@ -79,7 +79,7 @@ pub fn is_image_content_type(test: &str) -> Result<(), failure::Error> {
     .get("Content-Type")
     .ok_or_else(|| format_err!("No Content-Type header"))?
     .to_str()?
-    .starts_with("image")
+    .starts_with("image/")
   {
     Ok(())
   } else {