diff --git a/oauthex/oauth2.go b/oauthex/oauth2.go
index f876be03..cdda695b 100644
--- a/oauthex/oauth2.go
+++ b/oauthex/oauth2.go
@@ -13,6 +13,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"mime"
 	"net/http"
 	"net/url"
 	"strings"
@@ -57,7 +58,9 @@ func getJSON[T any](ctx context.Context, c *http.Client, url string, limit int64
 		return nil, fmt.Errorf("bad status %s", res.Status)
 	}
 	// Specs require application/json.
-	if ct := res.Header.Get("Content-Type"); ct != "application/json" {
+	ct := res.Header.Get("Content-Type")
+	mediaType, _, err := mime.ParseMediaType(ct)
+	if err != nil || mediaType != "application/json" {
 		return nil, fmt.Errorf("bad content type %q", ct)
 	}