diff --git a/cmd/kg/handlers.go b/cmd/kg/handlers.go
index 4213487..986b06c 100644
--- a/cmd/kg/handlers.go
+++ b/cmd/kg/handlers.go
@@ -126,6 +126,7 @@ func (h *graphHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		mimeType = "application/octet-stream"
 	}
 
+	w.Header().Add("content-type", mimeType)
 	w.Write(output)
 }