diff --git a/lib/serve.js b/lib/serve.js
index 09c807e4..4764a871 100644
--- a/lib/serve.js
+++ b/lib/serve.js
@@ -44,6 +44,23 @@ function promiseCallback(promise, callback) {
   );
 }
 
+function buildClientContext(headers) {
+  // inject a client context based on auth header https://github.com/netlify/netlify-lambda/pull/57
+  if (!headers['authorization']) return;
+
+  const parts = headers['authorization'].split(' ');
+  if (parts.length !== 2 || parts[0] !== 'Bearer') return;
+
+  try {
+    return {
+      identity: { url: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_URL', token: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_TOKEN' },
+      user: jwtDecode(parts[1])
+    };
+  } catch (e) {
+    return; // Ignore errors - bearer token is not a JWT, probably not intended for us
+  }
+}
+
 function createHandler(dir, static) {
   return function(request, response) {
     // handle proxies without path re-writes (http-servr)
@@ -77,19 +94,8 @@ function createHandler(dir, static) {
     };
 
     var callback = createCallback(response);
-    
-    // inject a client context based on auth header https://github.com/netlify/netlify-lambda/pull/57
-    let clientContext = {}
-    if (request.headers['authorization']) {
-      const parts = request.headers['authorization'].split(' ')
-      if (parts.length === 2 && parts[0] === 'Bearer') {
-        clientContext = {
-          identity: { url: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_URL', token: 'NETLIFY_LAMBDA_LOCALLY_EMULATED_IDENTITY_TOKEN' },
-          user: jwtDecode(parts[1])
-        }
-      }
-    }
-    var promise = handler.handler(lambdaRequest, { clientContext }, callback);
+
+    var promise = handler.handler(lambdaRequest, { clientContext: buildClientContext(request.headers) || {} }, callback);
     promiseCallback(promise, callback);
   };
 }