diff --git a/src/Back.cpp b/src/Back.cpp
index 5234400f..c01a448a 100644
--- a/src/Back.cpp
+++ b/src/Back.cpp
@@ -7,11 +7,7 @@
 
 #include "CommonDefines.h"
 #include "Draw.h"
-#include "Frame.h"
-#include "Game.h"
 #include "Main.h"
-#include "Map.h"
-#include "Stage.h"
 
 BACK gBack;
 int gWaterY;
diff --git a/src/Draw.cpp b/src/Draw.cpp
index 59aff022..4c30e934 100644
--- a/src/Draw.cpp
+++ b/src/Draw.cpp
@@ -2,7 +2,6 @@
 
 #include <stddef.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 
 #include <ddraw.h>
diff --git a/src/Input.cpp b/src/Input.cpp
index 2776b269..86905b6a 100644
--- a/src/Input.cpp
+++ b/src/Input.cpp
@@ -2,7 +2,6 @@
 
 #include <stddef.h>
 #include <stdio.h>
-#include <string.h>
 
 #if defined(_MSC_VER) && _MSC_VER >= 1500	// Newer versions of Visual Studio don't support anything earlier than DirectInput8
 #define DIRECTINPUT_VERSION 0x800
diff --git a/src/NpChar.h b/src/NpChar.h
index 0f2f9583..542619ee 100644
--- a/src/NpChar.h
+++ b/src/NpChar.h
@@ -1,6 +1,5 @@
 #pragma once
 
-#include "CommonDefines.h"
 #include "WindowsWrapper.h"
 
 #include "Draw.h"
diff --git a/src/Organya.cpp b/src/Organya.cpp
index f93394e2..069d7a59 100644
--- a/src/Organya.cpp
+++ b/src/Organya.cpp
@@ -7,7 +7,6 @@
 #include "Organya.h"
 
 #include <stddef.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -256,7 +255,7 @@ void ChangeOrganPan(unsigned char key, unsigned char pan, signed char track)	//
 	if (lpDS == NULL)
 		return;
 
-	if (old_key[track] != PANDUMMY)
+	if (old_key[track] != KEYDUMMY)
 		lpORGANBUFFER[track][old_key[track] / 12][key_twin[track]]->SetPan((pan_tbl[pan] - 0x100) * 10);
 }
 
@@ -265,7 +264,7 @@ void ChangeOrganVolume(int no, long volume, signed char track)	// 300がMAXで30
 	if (lpDS == NULL)
 		return;
 
-	if (old_key[track] != VOLDUMMY)
+	if (old_key[track] != KEYDUMMY)
 		lpORGANBUFFER[track][old_key[track] / 12][key_twin[track]]->SetVolume((volume - 0xFF) * 8);
 }
 
diff --git a/src/Sound.cpp b/src/Sound.cpp
index 40f1ff93..43be7281 100644
--- a/src/Sound.cpp
+++ b/src/Sound.cpp
@@ -12,7 +12,7 @@ equivalents.
 
 #include "Sound.h"
 
-#include <math.h>
+#include <stddef.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/src/Sound.h b/src/Sound.h
index 46a0e032..d1dc3c40 100644
--- a/src/Sound.h
+++ b/src/Sound.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include <stddef.h>
-
 #ifndef DIRECTSOUND_VERSION
 #define DIRECTSOUND_VERSION 0x500
 #endif