GL_LUMINANCE format for texture uploads in Android plugin

I am building a plugin for Android that requires I upload a texture from native code. To get the basic plugin framework set up, I wrote a small function that binds to a texture handle passed from Unity and uploads random noise to the GPU for this texture. The plugin will eventually provide a buffer of `GLubyte`s representing a grayscale image. To do the actual texture upload, I make the following OpenGL call:

 glTexImage2D(
     GL_TEXTURE_2D, 0,
     GL_LUMINANCE,
     width, height,
     0, GL_LUMINANCE,
     GL_UNSIGNED_BYTE, 
     data
 );

When doing this call, the result is a black texture on the mesh I am mapping it to. However, if I use `GL_RGBA` as the internal/external format and generate 4 times the amount of noise, the result is, as expected, noise.

Is there something I'm missing here. This works fine in regular OpenGL ES.

Thanks.