diff --git a/doc/src/region.rst b/doc/src/region.rst
index 7e3c95362c..a6a9469381 100644
--- a/doc/src/region.rst
+++ b/doc/src/region.rst
@@ -38,7 +38,7 @@ Syntax
        *plane* args = px py pz nx ny nz
          px,py,pz = point on the plane (distance units)
          nx,ny,nz = direction normal to plane (distance units)
-         px,py,pz can be a variable
+           px,py,pz can be a variable
        *prism* args = xlo xhi ylo yhi zlo zhi xy xz yz
          xlo,xhi,ylo,yhi,zlo,zhi = bounds of untilted prism (distance units)
          xy = distance to tilt y in x direction (distance units)