diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88169fb..3065138 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ Bug fixes:
 
 * [BUG #1581](https://github.com/BurntSushi/ripgrep/issues/1581):
   Corrects some egregious markup output in `--help`.
+* [BUG #1591](https://github.com/BurntSushi/ripgrep/issues/1591):
+  Mention the special `$0` capture group in docs for the `-r/--replace` flag.
 
 
 12.1.0 (2020-05-09)
diff --git a/crates/core/app.rs b/crates/core/app.rs
index 9535844..927b397 100644
--- a/crates/core/app.rs
+++ b/crates/core/app.rs
@@ -2576,10 +2576,13 @@ Replace every match with the text given when printing results. Neither this
 flag nor any other ripgrep flag will modify your files.
 
 Capture group indices (e.g., $5) and names (e.g., $foo) are supported in the
-replacement string. In shells such as Bash and zsh, you should wrap the
-pattern in single quotes instead of double quotes. Otherwise, capture group
-indices will be replaced by expanded shell variables which will most likely
-be empty.
+replacement string. Capture group indices are numbered based on the position of
+the opening paranthesis of the group, where the leftmost such group is $1. The
+special $0 group corresponds to the entire match.
+
+In shells such as Bash and zsh, you should wrap the pattern in single quotes
+instead of double quotes. Otherwise, capture group indices will be replaced by
+expanded shell variables which will most likely be empty.
 
 To write a literal '$', use '$$'.