diff --git a/relay/channel/openai/token.go b/relay/channel/openai/token.go
index 984ef4e8..32756f96 100644
--- a/relay/channel/openai/token.go
+++ b/relay/channel/openai/token.go
@@ -130,6 +130,9 @@ const (
 // https://platform.openai.com/docs/guides/vision/calculating-costs
 // https://github.com/openai/openai-cookbook/blob/05e3f9be4c7a2ae7ecf029a7c32065b024730ebe/examples/How_to_count_tokens_with_tiktoken.ipynb
 func countImageTokens(url string, detail string) (_ int, err error) {
+	if !strings.HasPrefix(url, "data:image") {
+        return 0, errors.New("invalid image file type")
+    }
 	var fetchSize = true
 	var width, height int
 	// Reference: https://platform.openai.com/docs/guides/vision/low-or-high-fidelity-image-understanding