diff --git a/IkiWiki/Render.pm b/IkiWiki/Render.pm
index a90d202ee..c41dac9f6 100644
--- a/IkiWiki/Render.pm
+++ b/IkiWiki/Render.pm
@@ -770,9 +770,17 @@ sub refresh () {
 	my ($new, $internal_new)=find_new_files($files);
 	my ($del, $internal_del)=find_del_files($pages);
 	my ($changed, $internal_changed)=find_changed($files);
+	my %existingfiles;
 	run_hooks(needsbuild => sub {
 		my $ret=shift->($changed, [@$del, @$internal_del]);
-		$changed=$ret if ref $ret eq 'ARRAY';
+		if (ref $ret eq 'ARRAY') {
+			if (! %existingfiles) {
+				foreach my $f (@$files) {
+					$existingfiles{$f}=1;
+				}
+			}
+			@$changed=grep $existingfiles{$_}, @$ret;
+		}
 	});
 	my $oldlink_targets=calculate_old_links($changed, $del);
 
diff --git a/debian/changelog b/debian/changelog
index 04feaffcb..c3f4db798 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -15,6 +15,8 @@ ikiwiki (3.20130519) UNRELEASED; urgency=low
     accessed via https.
   * The ip() pagespec can now contain glob characters to match eg, a subnet
     full of spammers.
+  * Fix crash that could occur when a needsbuild hook returned a file
+    that does not exist.
 
  -- Joey Hess <joeyh@debian.org>  Sun, 23 Jun 2013 14:02:01 -0400