diff --git a/lib/proxy.ts b/lib/proxy.ts
index 5a8154e..c62e419 100644
--- a/lib/proxy.ts
+++ b/lib/proxy.ts
@@ -1052,6 +1052,11 @@ export class Proxy implements IProxy {
           return self._onError("ON_RESPONSE_ERROR", ctx, err);
         }
         const servToProxyResp = ctx.serverToProxyResponse!;
+
+        if (servToProxyResp.headers["trailer"]) {
+          servToProxyResp.headers["transfer-encoding"] = "chunked";
+        }
+
         if (
           self.responseContentPotentiallyModified ||
           ctx.responseContentPotentiallyModified