diff --git a/girmodule.c b/girmodule.c
index 05c8987fc..e3897c34d 100644
--- a/girmodule.c
+++ b/girmodule.c
@@ -279,8 +279,9 @@ add_directory_index_section (guint8 *data, GIrModule *module, guint32 *offset2)
   alloc_section (data, GI_SECTION_DIRECTORY_INDEX, *offset2);
 
   required_size = _gi_typelib_hash_builder_get_buffer_size (dirindex_builder);
+  required_size = ALIGN_VALUE (required_size, 4);
 
-  new_offset = *offset2 + ALIGN_VALUE (required_size, 4);
+  new_offset = *offset2 + required_size;
 
   data = g_realloc (data, new_offset);
 
diff --git a/gthash.c b/gthash.c
index ecc3b1040..831c87e97 100644
--- a/gthash.c
+++ b/gthash.c
@@ -158,6 +158,8 @@ _gi_typelib_hash_builder_pack (GITypelibHashBuilder *builder, guint8* mem, guint
   g_assert (len >= builder->packed_size);
   g_assert ((((unsigned long)mem) & 0x3) == 0);
 
+  memset (mem, 0, len);
+
   *((guint32*) mem) = builder->dirmap_offset;
   packed_mem = (guint8*)(mem + sizeof(guint32));
   cmph_pack (builder->c, packed_mem);