diff --git a/cgit.h b/cgit.h
index a72c503..e6e7715 100644
--- a/cgit.h
+++ b/cgit.h
@@ -59,6 +59,7 @@ typedef enum {
 struct cgit_filter {
 	char *cmd;
 	char **argv;
+	int extra_args;
 	int old_stdout;
 	int pipe_fh[2];
 	int pid;
@@ -342,7 +343,7 @@ extern const char *cgit_repobasename(const char *reponame);
 
 extern int cgit_parse_snapshots_mask(const char *str);
 
-extern int cgit_open_filter(struct cgit_filter *filter);
+extern int cgit_open_filter(struct cgit_filter *filter, ...);
 extern int cgit_close_filter(struct cgit_filter *filter);
 extern struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype);
 
diff --git a/filter.c b/filter.c
index f4ee9ac..d8c0116 100644
--- a/filter.c
+++ b/filter.c
@@ -13,8 +13,16 @@
 #include <string.h>
 #include <stdlib.h>
 
-int cgit_open_filter(struct cgit_filter *filter)
+int cgit_open_filter(struct cgit_filter *filter, ...)
 {
+	int i;
+	va_list ap;
+
+	va_start(ap, filter);
+	for (i = 0; i < filter->extra_args; i++)
+		filter->argv[i+1] = va_arg(ap, char *);
+	va_end(ap);
+
 	filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
 		"Unable to duplicate STDOUT");
 	chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
@@ -36,45 +44,50 @@ int cgit_open_filter(struct cgit_filter *filter)
 
 int cgit_close_filter(struct cgit_filter *filter)
 {
-	int exit_status;
+	int i, exit_status;
 
 	chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
 		"Unable to restore STDOUT");
 	close(filter->old_stdout);
 	if (filter->pid < 0)
-		return 0;
+		goto done;
 	waitpid(filter->pid, &exit_status, 0);
 	if (WIFEXITED(exit_status) && !WEXITSTATUS(exit_status))
-		return 0;
+		goto done;
 	die("Subprocess %s exited abnormally", filter->cmd);
+
+done:
+	for (i = 0; i < filter->extra_args; i++)
+		filter->argv[i+1] = NULL;
+	return 0;
+
 }
 
 struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
 {
 	struct cgit_filter *f;
 	int args_size = 0;
-	int extra_args;
 
 	if (!cmd || !cmd[0])
 		return NULL;
 
+	f = xmalloc(sizeof(struct cgit_filter));
+	memset(f, 0, sizeof(struct cgit_filter));
+
 	switch (filtertype) {
 		case SOURCE:
 		case ABOUT:
-			extra_args = 1;
+			f->extra_args = 1;
 			break;
 
 		case COMMIT:
 		default:
-			extra_args = 0;
+			f->extra_args = 0;
 			break;
 	}
-	
-	f = xmalloc(sizeof(struct cgit_filter));
-	memset(f, 0, sizeof(struct cgit_filter));
 
 	f->cmd = xstrdup(cmd);
-	args_size = (2 + extra_args) * sizeof(char *);
+	args_size = (2 + f->extra_args) * sizeof(char *);
 	f->argv = xmalloc(args_size);
 	memset(f->argv, 0, args_size);
 	f->argv[0] = f->cmd;
diff --git a/ui-repolist.c b/ui-repolist.c
index d4ee279..f622a01 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -331,13 +331,9 @@ void cgit_print_site_readme()
 {
 	if (!ctx.cfg.root_readme)
 		return;
-	if (ctx.cfg.about_filter) {
-		ctx.cfg.about_filter->argv[1] = ctx.cfg.root_readme;
-		cgit_open_filter(ctx.cfg.about_filter);
-	}
+	if (ctx.cfg.about_filter)
+		cgit_open_filter(ctx.cfg.about_filter, ctx.cfg.root_readme);
 	html_include(ctx.cfg.root_readme);
-	if (ctx.cfg.about_filter) {
+	if (ctx.cfg.about_filter)
 		cgit_close_filter(ctx.cfg.about_filter);
-		ctx.cfg.about_filter->argv[1] = NULL;
-	}
 }
diff --git a/ui-summary.c b/ui-summary.c
index 63a5a75..725f3ab 100644
--- a/ui-summary.c
+++ b/ui-summary.c
@@ -151,18 +151,17 @@ void cgit_print_repo_readme(char *path)
 	 * filesystem, while applying the about-filter.
 	 */
 	html("<div id='summary'>");
-	if (ctx.repo->about_filter) {
-		ctx.repo->about_filter->argv[1] = filename;
-		cgit_open_filter(ctx.repo->about_filter);
-	}
+	if (ctx.repo->about_filter)
+		cgit_open_filter(ctx.repo->about_filter, filename);
+
 	if (ref)
 		cgit_print_file(filename, ref, 1);
 	else
 		html_include(filename);
-	if (ctx.repo->about_filter) {
+
+	if (ctx.repo->about_filter)
 		cgit_close_filter(ctx.repo->about_filter);
-		ctx.repo->about_filter->argv[1] = NULL;
-	}
+
 	html("</div>");
 	if (free_filename)
 		free(filename);
diff --git a/ui-tree.c b/ui-tree.c
index 5ae3926..e4c3d22 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -45,13 +45,12 @@ static void print_text_buffer(const char *name, char *buf, unsigned long size)
 	}
 
 	if (ctx.repo->source_filter) {
+		char *filter_arg = xstrdup(name);
 		html("<td class='lines'><pre><code>");
-		ctx.repo->source_filter->argv[1] = xstrdup(name);
-		cgit_open_filter(ctx.repo->source_filter);
+		cgit_open_filter(ctx.repo->source_filter, filter_arg);
 		html_raw(buf, size);
 		cgit_close_filter(ctx.repo->source_filter);
-		free(ctx.repo->source_filter->argv[1]);
-		ctx.repo->source_filter->argv[1] = NULL;
+		free(filter_arg);
 		html("</code></pre></td></tr></table>\n");
 		return;
 	}