diff --git a/IkiWiki/Plugin/sidebar.pm b/IkiWiki/Plugin/sidebar.pm
index 1b302dcf9..f706480ca 100644
--- a/IkiWiki/Plugin/sidebar.pm
+++ b/IkiWiki/Plugin/sidebar.pm
@@ -23,7 +23,7 @@ sub getsetup () {
 		global_sidebars => {
 			type => "boolean",
 			examples => 1,
-			description => "show sidebar page on all pages?"
+			description => "show sidebar page on all pages?",
 			safe => 1,
 			rebuild => 1,
 		},
@@ -36,20 +36,22 @@ sub preprocess (@) {
 	my $content=shift;
 	shift;
 
-	if (! defined $content) {
-		error(gettext("sidebar content not specified"));
-	}
-
 	my $page=$params{page};
 	return "" unless $page eq $params{destpage};
-	my $file = $pagesources{$page};
-	my $type = pagetype($file);
+	
+	if (! defined $content) {
+		$pagesidebar{$page}=undef;
+	}
+	else {
+		my $file = $pagesources{$page};
+		my $type = pagetype($file);
 
-	$pagesidebar{$page}=
-		IkiWiki::htmlize($page, $page, $type,
-		IkiWiki::linkify($page, $page,
-		IkiWiki::preprocess($page, $page,
-		IkiWiki::filter($page, $page, $content))));
+		$pagesidebar{$page}=
+			IkiWiki::htmlize($page, $page, $type,
+			IkiWiki::linkify($page, $page,
+			IkiWiki::preprocess($page, $page,
+			IkiWiki::filter($page, $page, $content))));
+	}
 
 	return "";
 }
@@ -60,9 +62,10 @@ my $oldcontent;
 sub sidebar_content ($) {
 	my $page=shift;
 	
-	return $pagesidebar{$page} if exists $pagesidebar{$page};
+	return $pagesidebar{$page} if defined $pagesidebar{$page};
 
-	return if defined $config{global_sidebars} && !$config{global_sidebars};
+	return if ! exists $pagesidebar{$page} && 
+		defined $config{global_sidebars} && ! $config{global_sidebars};
 
 	my $sidebar_page=bestlink($page, "sidebar") || return;
 	my $sidebar_file=$pagesources{$sidebar_page} || return;
diff --git a/doc/examples/blog/index.mdwn b/doc/examples/blog/index.mdwn
index 062c71f2e..a22c40c72 100644
--- a/doc/examples/blog/index.mdwn
+++ b/doc/examples/blog/index.mdwn
@@ -1,14 +1,6 @@
 [[!inline pages="./posts/* and !*/Discussion" show="10"
 actions=yes rootpage="posts"]]
 
-[[!sidebar """
-[[Tags]]: [[!pagestats style="list" pages="./tags/*" among="./posts/*"]]
-
-[[Recent Comments|comments]]
-
-[[Archives]]
-
-[[!calendar pages="./posts/* and !*/Discussion"]]
-"""]]
+[[!sidebar]]
 
 This blog is powered by [ikiwiki](http://ikiwiki.info).
diff --git a/doc/examples/blog/sidebar.mdwn b/doc/examples/blog/sidebar.mdwn
new file mode 100644
index 000000000..f24a8e57a
--- /dev/null
+++ b/doc/examples/blog/sidebar.mdwn
@@ -0,0 +1,9 @@
+[[Tags]]: [[!pagestats style="list" pages="./tags/*" among="./posts/*"]]
+
+[[Recent Comments|comments]]
+
+[[Archives]]
+
+[[!if "enabled(calendar)" then="""
+[[!calendar pages="./posts/* and !*/Discussion"]]
+"""]]
diff --git a/doc/ikiwiki/directive/sidebar.mdwn b/doc/ikiwiki/directive/sidebar.mdwn
index 34f078672..401d7c786 100644
--- a/doc/ikiwiki/directive/sidebar.mdwn
+++ b/doc/ikiwiki/directive/sidebar.mdwn
@@ -1,8 +1,12 @@
 The `sidebar` directive is supplied by the [[!iki plugins/sidebar desc=sidebar]] plugin.
 
-This directive specifies a custom sidebar to display on the page,
+This directive can specify a custom sidebar to display on the page,
 overriding any sidebar that is displayed globally.
 
+If no custom sidebar content is specified, it forces the sidebar page to
+be used as the sidebar, even if the `global_sidebars` setting has been
+used to disable use of the sidebar page by default.
+
 ## examples
 
 	\[[!sidebar """
@@ -11,4 +15,6 @@ overriding any sidebar that is displayed globally.
 	\[[!calendar pages="posts/*"]]
 	"""]]
 
+	\[[!sidebar]]
+
 [[!meta robots="noindex, follow"]]