diff --git a/app/server.go b/app/server.go
index ddbc09beb..9f6f8b07f 100644
--- a/app/server.go
+++ b/app/server.go
@@ -234,8 +234,8 @@ func grpcHandlerFunc(grpcServer *grpc.Server, otherHandler http.Handler) http.Ha
 
 func makeHeaderMatcher(c *Config) func(key string) (string, bool) {
 	return func(key string) (string, bool) {
-		switch key {
-		case c.AuthenticatedUserHeaderKey:
+		switch strings.ToLower(key) {
+		case strings.ToLower(c.AuthenticatedUserHeaderKey):
 			return key, true
 		default:
 			return runtime.DefaultHeaderMatcher(key)