diff --git a/IkiWiki/Plugin/graphviz.pm b/IkiWiki/Plugin/graphviz.pm
index bec122076..c91c92fec 100644
--- a/IkiWiki/Plugin/graphviz.pm
+++ b/IkiWiki/Plugin/graphviz.pm
@@ -79,12 +79,7 @@ sub render_graph (\%) {
 		}
 	}
 
-	if ($params{preview}) {
-		return "<img src=\"".urlto($dest, "")."\" />\n";
-	}
-	else {
-		return "<img src=\"".urlto($dest, $params{destpage})."\" />\n";
-	}
+	return "<img src=\"".urlto($dest, $params{destpage})."\" />\n";
 }
 
 sub graph (@) {
diff --git a/debian/changelog b/debian/changelog
index 9fb9607a3..31deaf9aa 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -11,6 +11,7 @@ ikiwiki (3.20100502) UNRELEASED; urgency=low
     (COMMENTSLINK and DISCUSSIONLINK could be folded into this, but
     are kept separate for now to avoid breaking modified templates.)
   * websetup: Only display Setup button on admins' preferences page. 
+  * graphviz: Fix display of preexisting images in preview mode.
 
  -- Joey Hess <joeyh@debian.org>  Sun, 02 May 2010 13:22:50 -0400
 
diff --git a/doc/bugs/Problems_with_graphviz.pm_plug-in_previews.mdwn b/doc/bugs/Problems_with_graphviz.pm_plug-in_previews.mdwn
index 283a6ef08..c77bbeeaf 100644
--- a/doc/bugs/Problems_with_graphviz.pm_plug-in_previews.mdwn
+++ b/doc/bugs/Problems_with_graphviz.pm_plug-in_previews.mdwn
@@ -44,3 +44,11 @@
 >>> case from the root of the site). The browsers appear to be trying to fetch
 >>> `/demo/diagrams/demo/diagrams/graph-c9fd2a197322feb417bdedbca5e99f5aa65b3f06.png`
 >>> (i.e., prepending the required relpath twice). -- [[Jon]]
+
+>>>> Yeah, that patch may have been right once, but it's wrong now;
+>>>> preview mode uses `<base>` to make urls work the same as they would
+>>>> when viewing the html page. 
+>>>>
+>>>> Perhaps this was not noticed for a while while because it only
+>>>> shows up if previewing an *unchanged* graph on a page that has already
+>>>> been built before. Fixed now. [[done]] --[[Joey]]