diff --git a/chapters/primsrast.txt b/chapters/primsrast.txt
index b8093a80..9d232e8b 100644
--- a/chapters/primsrast.txt
+++ b/chapters/primsrast.txt
@@ -1152,7 +1152,7 @@ is guaranteed to remain distinct throughout polygon rasterization and in the
 depth buffer.
 All pairs of fragments generated by the rasterization of two polygons with
 otherwise identical vertices, but [eq]#pname:z~f~# values that differ by
-$r$, will have distinct depth values.
+[eq]#r#, will have distinct depth values.
 
 For fixed-point depth buffer representations, [eq]#r# is constant throughout
 the range of the entire depth buffer.