Trying to implement JWT authentication in node. Getting unauthorized in protected routes

I am trying to implement JWT authentication. /login and /register work fine and they return authentication token, but when I try to GET /secret with a header 'Authorization' = 'JWT token_received', it returns a string 'unauthorized' and I can see no logging from JWTStrategy. Please let me know where I am going wrong.

var opts = {}
opts.jwtFromRequest = ExtractJwt.fromAuthHeaderAsBearerToken();
opts.secretOrKey = "very_secret"

passport.use(new JwtStrategy(opts, function(payload, next){
    console.log("payload received" + payload);
    User.findById(payload.id, function(err, user){
        console.log("user found:" + user);
        if(err){
            return next(err, false)
        }
        else if(user){
            return next(null, user)
        }
        else{
            return next(null, false)
        }
    });
    }
));

app.use(passport.initialize());

app.post("/login", function(req, res){

        var email = req.body.email;
        var password = req.body.password;

        var user = User.findOne({"email": email}, function(err, user){

        if(err){
            res.json({"error": err});
            return;
        }
        if(!user){
            res.json({"message": "No user found"});
            return;
        }
        if(user.password == password){
            res.json(
                { 
                    "message": "User found",
                    "token": jwt.sign({"id": user.id}, opts.secretOrKey)
                }
            );
        }
        else{
            res.json({"message": "Password did not match"});
        }
    });
});

app.post("/register", function(req, res){
new User({ email: req.body.email, password: req.body.password}).
    save(function(err, user){
            if(err){
                res.json({"message": "User cannot be created"});
            }
            else{
                res.json(
                    { 
                        "message": "ok",
                        "token": jwt.sign({"id": user.id}, opts.secretOrKey)
                    }
                );
            }
    });
});

app.get("/secret", passport.authenticate("jwt", {session: false}), function(req, res){
    console.log(req.get('Authorization'));
    res.json(req.user);
});

Using postman as the client. Request details from postman,

GET /secret HTTP/1.1
Host: localhost:3000
Content-Type: application/x-www-form-urlencoded
Authorization: JWT token_I_received_on_login
Cache-Control: no-cache
Postman-Token: 114060a3-3074-6688-6245-0b0cfe7e9f04