diff --git a/doc_src/test.txt b/doc_src/test.txt
index 632e7901a..64a6f4710 100644
--- a/doc_src/test.txt
+++ b/doc_src/test.txt
@@ -3,12 +3,15 @@
 \subsection test-synopsis Synopsis
 \fish{synopsis}
 test [EXPRESSION]
+[ [EXPRESSION] ]
 \endfish
 
 \subsection test-description Description
 
 Tests the expression given and sets the exit status to 0 if true, and 1 if false. An expression is made up of one or more operators and their arguments.
 
+The first form (`test`) is preferred. For compatibility with other shells, the second form is available: a matching pair of square brackets (`[ [EXPRESSION ] ]`).
+
 The following operators are available to examine files and directories:
 
 - `-b FILE` returns true if `FILE` is a block device.