diff --git a/github.go b/github.go
index d3a9498..75635b7 100644
--- a/github.go
+++ b/github.go
@@ -44,7 +44,7 @@ func NewGitHub(client ApiClient) *GitHub {
 }
 
 func HasContentType(r *http.Response, mimetype string) bool {
-	contentType := r.Header.Get("Content-type")
+	contentType := r.Header.Get("content-type")
 	if contentType == "" {
 		return mimetype == "application/octet-stream"
 	}