使用依赖项的修改版本时，Go会抱怨类型错误

I'm using dep to manage dependencies in my Go project.

I have a simple project in ~/go/src/github.com/my-repo/myproject, with one file example.go:

package main

import (
    tcrypto "github.com/tendermint/go-crypto"
    "github.com/tendermint/tendermint/types"
)

type ExampleSigner struct{}

// Implements types.Signer
func (signer ExampleSigner) Sign(msg []byte) tcrypto.Signature {
    return tcrypto.Signature{}
}

// Implements types.Signer
func (signer ExampleSigner) PubKey() tcrypto.PubKey {
    return tcrypto.PubKey{}
}

func main() {
    mySigner := ExampleSigner{}
    validator := types.LoadPrivValidator("foo")
    validator.SetSigner(mySigner)
}

Running dep init, then dep ensure, then go install works fine. (Running the code won't do anything meaningful - this is just enough code to reproduce the compilation error below).

Now, I want to use a modified version of github.com/tendermint/tendermint, so per the documentation, I've removed the directory from ./vendor and have a modified copy in my $GOPATH:

~/go/src/github.com/tendermint/tendermint    <---- (modified copy)
~/go/src/github.com/my-repo/myproject/vendor/github.com/tendermint/tendermint
                                                                   ^^^^^^^^^^
                                                          (I deleted this directory)

I now get the following compilation errors, assuming I've installed the tendermint/tendermint dependencies using glide install:

# github.com/my-repo/myproject
./example.go:25:21: cannot use mySigner (type ExampleSigner) as type "github.com/tendermint/tendermint/types".Signer in argument to validator.SetSigner:
    ExampleSigner does not implement "github.com/tendermint/tendermint/types".Signer (wrong type for PubKey method)
        have PubKey() "github.com/my-repo/myproject/vendor/github.com/tendermint/go-crypto".PubKey
        want PubKey() "github.com/tendermint/tendermint/vendor/github.com/tendermint/go-crypto".PubKey

If I delete the ~/go/src/github.com/tendermint/tendermint/vendor directory, I then get these errors instead:

../../tendermint/tendermint/types/events.go:5:2: cannot find package "github.com/tendermint/abci/types" in any of:
    /usr/local/go/src/github.com/tendermint/abci/types (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/abci/types (from $GOPATH)
../../tendermint/tendermint/types/genesis.go:10:2: cannot find package "github.com/tendermint/go-crypto" in any of:
    /usr/local/go/src/github.com/tendermint/go-crypto (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/go-crypto (from $GOPATH)
../../tendermint/tendermint/types/block.go:11:2: cannot find package "github.com/tendermint/go-wire" in any of:
    /usr/local/go/src/github.com/tendermint/go-wire (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/go-wire (from $GOPATH)
../../tendermint/tendermint/types/block.go:12:2: cannot find package "github.com/tendermint/go-wire/data" in any of:
    /usr/local/go/src/github.com/tendermint/go-wire/data (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/go-wire/data (from $GOPATH)
../../tendermint/tendermint/types/block.go:13:2: cannot find package "github.com/tendermint/tmlibs/common" in any of:
    /usr/local/go/src/github.com/tendermint/tmlibs/common (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/tmlibs/common (from $GOPATH)
../../tendermint/tendermint/types/events.go:8:2: cannot find package "github.com/tendermint/tmlibs/events" in any of:
    /usr/local/go/src/github.com/tendermint/tmlibs/events (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/tmlibs/events (from $GOPATH)
../../tendermint/tendermint/types/priv_validator.go:15:2: cannot find package "github.com/tendermint/tmlibs/log" in any of:
    /usr/local/go/src/github.com/tendermint/tmlibs/log (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/tmlibs/log (from $GOPATH)
../../tendermint/tendermint/types/block.go:14:2: cannot find package "github.com/tendermint/tmlibs/merkle" in any of:
    /usr/local/go/src/github.com/tendermint/tmlibs/merkle (from $GOROOT)
    /home/djones/go/src/github.com/tendermint/tmlibs/merkle (from $GOPATH)

Is there any way to avoid these errors, without having to commit my modified tendermint/tendermint to a repo somewhere and use source in my Gopkg.toml?