diff --git a/man/git-pr.1 b/man/git-pr.1
index 4c03d00..490cf98 100644
--- a/man/git-pr.1
+++ b/man/git-pr.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "GIT\-PR" "1" "June 2019" "" "Git Extras"
+.TH "GIT\-PR" "1" "August 2019" "" "Git Extras"
 .
 .SH "NAME"
 \fBgit\-pr\fR \- Checks out a pull request locally
@@ -31,7 +31,7 @@ GitHub pull request URL in the format \fBhttps://github\.com/tj/git\-extras/pull
 \-m | \-\-merge
 .
 .P
-Checkout a merge commit against the branch the pull request is targeting\.
+Checkout a merge commit against the branch the pull request is targeting\. Because this feature uses a private API with which GitHub checks the pull request\'s mergeability, it only works with the opened pull request\. If the merge commit is not up\-to\-date, please visit the pull request web page to trigger the rebuild\.
 .
 .SH "EXAMPLES"
 This checks out the pull request \fB226\fR from \fBorigin\fR:
diff --git a/man/git-pr.html b/man/git-pr.html
index f4649ef..eb2eb3a 100644
--- a/man/git-pr.html
+++ b/man/git-pr.html
@@ -98,7 +98,11 @@
 
 <p>  -m | --merge</p>
 
-<p>  Checkout a merge commit against the branch the pull request is targeting.</p>
+<p>  Checkout a merge commit against the branch the pull request is targeting.
+  Because this feature uses a private API with which GitHub checks the pull
+  request's mergeability, it only works with the opened pull request. If the merge
+  commit is not up-to-date, please visit the pull request web page to trigger the
+  rebuild.</p>
 
 <h2 id="EXAMPLES">EXAMPLES</h2>
 
@@ -190,7 +194,7 @@ Deleted branch pr/775 (was de6e51c).
 
   <ol class='man-decor man-foot man foot'>
     <li class='tl'></li>
-    <li class='tc'>June 2019</li>
+    <li class='tc'>August 2019</li>
     <li class='tr'>git-pr(1)</li>
   </ol>
 
diff --git a/man/git-pr.md b/man/git-pr.md
index 72c97fe..d554c55 100644
--- a/man/git-pr.md
+++ b/man/git-pr.md
@@ -26,6 +26,10 @@ git-pr(1) -- Checks out a pull request locally
   -m | --merge
 
   Checkout a merge commit against the branch the pull request is targeting.
+  Because this feature uses a private API with which GitHub checks the pull
+  request's mergeability, it only works with the opened pull request. If the merge
+  commit is not up-to-date, please visit the pull request web page to trigger the
+  rebuild.
 
 ## EXAMPLES