diff --git a/gdb/nacl-manifest.c b/gdb/nacl-manifest.c
index 5627d26..c32c98c 100644
--- a/gdb/nacl-manifest.c
+++ b/gdb/nacl-manifest.c
@@ -118,7 +118,9 @@
 nacl_manifest_free (void)
 {
   nacl_manifest_free_list(nacl_file_list_32);
+  nacl_file_list_32 = NULL;
   nacl_manifest_free_list(nacl_file_list_64);
+  nacl_file_list_64 = NULL;
   xfree (nacl_program_filename_32);
   xfree (nacl_program_filename_64);
   nacl_program_filename_32 = NULL;