diff --git a/notmuch.1 b/notmuch.1
index 0e6a2edc..96fd2429 100644
--- a/notmuch.1
+++ b/notmuch.1
@@ -387,6 +387,9 @@ which will match all messages that contain all of the given
 terms/phrases in the body, the subject, or any of the sender or
 recipient headers.
 
+As a special case, a search string consisting of exactly a single
+asterisk ("*") will match all messages.
+
 In addition to free text, the following prefixes can be used to force
 terms to match against specific portions of an email, (where
 <brackets> indicate user-supplied values):
diff --git a/notmuch.c b/notmuch.c
index 86509515..7e595e24 100644
--- a/notmuch.c
+++ b/notmuch.c
@@ -44,6 +44,9 @@ static const char search_terms_help[] =
     "\tthe given terms/phrases in the body, the subject, or any of\n"
     "\tthe sender or recipient headers.\n"
     "\n"
+    "\tAs a special case, a search string consisting of exactly a\n"
+    "\tsingle asterisk (\"*\") will match all messages.\n"
+    "\n"
     "\tIn addition to free text, the following prefixes can be used\n"
     "\tto force terms to match against specific portions of an email,\n"
     "\t(where <brackets> indicate user-supplied values):\n"