Extruding square shape (from mesh) along curve results in a flattened mesh I'm trying to extrude a simple square shape along a curve, with the view to making a set of steps go around a corner.

Extruding a circle works perfectly, but a square shape seems to extrude along the Y axis instead of the X and is therefore just a flat shape.

Steps
- Created cube shape


Selected 1 face and duplicated it
Separated the face so it is a single object
Transform/rotation applied
Alt+C - converted mesh to curve
Added Path
Gone to path object panel > Geometry and selected the 'Bevel Object' to be the square


Result

The Extrusion is a flattened mesh.

Doing the exact same steps with a cylinder works just fine.

Blend file here - http://pasteall.org/blend/index.php?id=47161

Many thanks in advance.
The problem is your object called "square". It does not have the same orientation as the "Cylinder.001" that you used to extrude the Cylinder. The curve will be extruded on the local Z axis so make sure its facing the direction of extrusion.
A quick fix is to open the object "square" in Edit Mode and rotate it on the Y axis by 90°.