diff --git a/sysdeps/linux/fsusage.c b/sysdeps/linux/fsusage.c
index 559ba1f9..13564948 100644
--- a/sysdeps/linux/fsusage.c
+++ b/sysdeps/linux/fsusage.c
@@ -140,7 +140,7 @@ static void linux_2_6_0(glibtop *server, glibtop_fsusage *buf, const char *path)
 
 	get_sys_path(server, device, &filename, &format);
 
-	ret = try_file_to_buffer(buffer, sizeof buffer, filename);
+	ret = try_file_to_buffer(buffer, sizeof buffer, "%s", filename);
 
 	if (ret < 0) goto out;
 
diff --git a/sysdeps/linux/glibtop_private.c b/sysdeps/linux/glibtop_private.c
index 041624c7..52c3782c 100644
--- a/sysdeps/linux/glibtop_private.c
+++ b/sysdeps/linux/glibtop_private.c
@@ -124,7 +124,7 @@ int try_file_to_buffer(char *buffer, size_t bufsiz, const char *format, ...)
 void
 file_to_buffer(glibtop *server, char *buffer, size_t bufsiz, const char *filename)
 {
-	switch(try_file_to_buffer(buffer, bufsiz, filename))
+	switch(try_file_to_buffer(buffer, bufsiz, "%s", filename))
 	{
 	case TRY_FILE_TO_BUFFER_OPEN:
 		glibtop_error_io_r (server, "open (%s)", filename);