diff --git a/build/libraries_sysmenu/dht/common/src/dht.c b/build/libraries_sysmenu/dht/common/src/dht.c
index 4d2e3848..97aff406 100644
--- a/build/libraries_sysmenu/dht/common/src/dht.c
+++ b/build/libraries_sysmenu/dht/common/src/dht.c
@@ -114,7 +114,7 @@ u32 DHT_GetDatabaseLength(const DHTFile* pDHT)
     }
     return sizeof(DHTHeader) + pDHT->header.nums * sizeof(DHTDatabase);
 }
-BOOL DHT_CheckDatabase(const DHTFile* pDHT)
+static BOOL DHT_CheckDatabase(const DHTFile* pDHT)
 {
     SVCSignHeapContext pool;
     u8 heap[4*1024];
@@ -143,7 +143,6 @@ BOOL DHT_PrepareDatabase(DHTFile* pDHT, FSFile* fp)
 {
     s32 result;
     s32 length;
-    u8 title[4] = { 'H','N','G','A' };
     PROFILE_INIT();
 
     if ( fp )
@@ -407,6 +406,11 @@ BOOL DHT_CheckHashPhase2(const u8* hash, const ROM_Header_Short* pROMHeader, DHT
             {
                 length = max_sectors;
             }
+            if ( length < 0 || offset < sizeof(ROM_Header) )
+            {
+                OS_TPrintf("Broaken FAT for %d of overlay.\n", i);
+                return FALSE;
+            }
             if ( !ImageHMACSHA1Update(&ctx, offset, length * 512) )
             {
                 OS_TPrintf("Cannot calc HMAC-SHA1 for %d of overlay.\n", i);
diff --git a/include/sysmenu/dht/dht.h b/include/sysmenu/dht/dht.h
index 1cb2457b..7fec7896 100644
--- a/include/sysmenu/dht/dht.h
+++ b/include/sysmenu/dht/dht.h
@@ -48,17 +48,6 @@ typedef BOOL    (*DHTReadFunc)(void* dest, s32 offset, s32 length, void* arg);
  *---------------------------------------------------------------------------*/
 u32 DHT_GetDatabaseLength(const DHTFile* pDHT);
 
-/*---------------------------------------------------------------------------*
-  Name:         DHT_PrepareDatabase
-
-  Description:  読み込み済みの全データベースの署名を検証する
-
-  Arguments:    pDHT        データベースの格納先
-
-  Returns:      成功すればTRUE
- *---------------------------------------------------------------------------*/
-BOOL DHT_CheckDatabase(const DHTFile* pDHT);
-
 /*---------------------------------------------------------------------------*
   Name:         DHT_PrepareDatabase