How do I use texSubImage2D to show sprites in webgl?

I can display my entire sprite (32x512) successfully with this call to gl.texImage2D:

gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);

It's squished horizontally, like I expected, but it renders on the screen at least. I'm trying to only display the first 32x32 sprite in the sheet and I assumed that I could simply use gl.texSubImage2D to achieve this effect. I tried a simple replacement of texImage2D with texSubImage2D (with modified parameters) but I just get a black box on the screen. Here's the code I'm using:

gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 32, 32, gl.RGBA, gl.UNSIGNED_BYTE, image);

Am I missing something about the implementation of texSubImage2D? Is there some other step I have to do? Or is texSubImage2D not the right way to do sprite sheets?