diff --git a/th04/main/boss/reset.cpp b/th04/main/boss/reset.cpp
index 7b02617d6..467c26992 100644
--- a/th04/main/boss/reset.cpp
+++ b/th04/main/boss/reset.cpp
@@ -2,7 +2,7 @@ char boss_phase_timed_out = 0;
 
 void pascal near boss_reset(void)
 {
-	boss_update = nullsub_1;
+	boss_update = nullfunc_far;
 	boss_fg_render = nullfunc_near;
 #if GAME == 5
 	boss_custombullets_render = nullfunc_near;
diff --git a/th04/main/null.asm b/th04/main/null.asm
new file mode 100644
index 000000000..ee6e06709
--- /dev/null
+++ b/th04/main/null.asm
@@ -0,0 +1,12 @@
+public NULLFUNC_NEAR
+nullfunc_near	proc near
+	retn
+nullfunc_near	endp
+	even
+
+
+public NULLFUNC_FAR
+nullfunc_far	proc far
+	retf
+nullfunc_far	endp
+	even
diff --git a/th04/main/null.hpp b/th04/main/null.hpp
new file mode 100644
index 000000000..b2dd5c485
--- /dev/null
+++ b/th04/main/null.hpp
@@ -0,0 +1,3 @@
+// Null functions for disabling callbacks
+void pascal near nullfunc_near(void);
+void pascal  far nullfunc_far(void);
diff --git a/th04_main.asm b/th04_main.asm
index 609924338..964b051f4 100644
--- a/th04_main.asm
+++ b/th04_main.asm
@@ -1719,27 +1719,8 @@ include th04/main/scroll_y_1.asm
 MOTION_UPDATE_DEF 1
 include th03/math/randring_fill.asm
 RANDRING_NEXT_DEF 1
-	nop
-
-; =============== S U B	R O U T	I N E =======================================
-
-public NULLFUNC_NEAR
-nullfunc_near	proc near
-		retn
-nullfunc_near	endp
-
-; ---------------------------------------------------------------------------
-		nop
-
-; =============== S U B	R O U T	I N E =======================================
-
-
-nullsub_2	proc far
-		retf
-nullsub_2	endp
-
-; ---------------------------------------------------------------------------
-		nop
+	even
+include th04/main/null.asm
 include th04/main/pointnum/inv_upd.asm
 include th04/main/pointnum/render.asm
 include th04/main/pointnum/num_put.asm
@@ -18036,7 +18017,7 @@ var_2		= word ptr -2
 loc_16638:
 		cmp	_boss_phase_frame, 0
 		jnz	short loc_16651
-		setfarfp	_stage_vm, nullsub_2
+		setfarfp	_stage_vm, nullfunc_far
 		mov	_midboss_frames_until, 0
 
 loc_16651:
@@ -20771,7 +20752,7 @@ loc_17E18:
 		les	bx, _std_ip
 		cmp	word ptr es:[bx], 0
 		jnz	short locret_17E3C
-		setfarfp	_stage_vm, nullsub_2
+		setfarfp	_stage_vm, nullfunc_far
 
 locret_17E3C:
 		leave
@@ -21899,7 +21880,7 @@ loc_18706:
 loc_1872F:
 		cmp	_boss_phase_frame, 0
 		jnz	short loc_1876B
-		setfarfp	_stage_vm, nullsub_2
+		setfarfp	_stage_vm, nullfunc_far
 		mov	_midboss_frames_until, 0
 		mov	fp_259E8, offset sub_180BB
 		mov	byte_259EF, 0
@@ -24474,7 +24455,7 @@ sub_19EBC	proc far
 		mov	bp, sp
 		mov	_midboss_invalidate?, offset nullfunc_near
 		mov	_midboss_render, offset nullfunc_near
-		setfarfp	_midboss_update, nullsub_2
+		setfarfp	_midboss_update, nullfunc_far
 		mov	_midboss_active, 0
 		mov	_midboss_hp, 0
 		pop	bp
@@ -26621,7 +26602,7 @@ var_2		= word ptr -2
 loc_1B497:
 		cmp	_boss_phase_frame, 0
 		jnz	short loc_1B4BA
-		setfarfp	_stage_vm, nullsub_2
+		setfarfp	_stage_vm, nullfunc_far
 		mov	_midboss_frames_until, 0
 		mov	byte_25A08, 0
 		mov	byte_25A1B, 0
@@ -31698,7 +31679,7 @@ items_update	endp
 boss_reset	proc near
 		push	bp
 		mov	bp, sp
-		setfarfp	_boss_update, nullsub_2
+		setfarfp	_boss_update, nullfunc_far
 		mov	_boss_fg_render, offset nullfunc_near
 		mov	_boss_phase, 0
 		mov	_boss_mode, 0
@@ -31941,7 +31922,7 @@ stage4_setup	endp
 stage5_setup	proc far
 		push	bp
 		mov	bp, sp
-		setfarfp	_midboss_update_func, nullsub_2
+		setfarfp	_midboss_update_func, nullfunc_far
 		mov	_midboss_render_func, offset nullfunc_near
 		mov	_midboss_frames_until, 60000
 		call	boss_reset
@@ -31980,7 +31961,7 @@ stage5_setup	endp
 stage6_setup	proc far
 		push	bp
 		mov	bp, sp
-		setfarfp	_midboss_update_func, nullsub_2
+		setfarfp	_midboss_update_func, nullfunc_far
 		mov	_midboss_render_func, offset nullfunc_near
 		mov	_midboss_frames_until, 60000
 		call	boss_reset
diff --git a/th05/main/stage/setup.cpp b/th05/main/stage/setup.cpp
index 5e7bf6ee4..bb79a3f81 100644
--- a/th05/main/stage/setup.cpp
+++ b/th05/main/stage/setup.cpp
@@ -153,7 +153,7 @@ void pascal near stage5_setup(void)
 
 void pascal near stage6_setup(void)
 {
-	midboss_update_func = nullsub_1;
+	midboss_update_func = nullfunc_far;
 	midboss_render_func = nullfunc_near;
 	midboss.frames_until = 30000;
 
diff --git a/th05/main012.cpp b/th05/main012.cpp
index 1c2d8e172..af344c12d 100644
--- a/th05/main012.cpp
+++ b/th05/main012.cpp
@@ -7,12 +7,10 @@
 
 extern "C" {
 #include "th05/th05.hpp"
+#include "th04/main/null.hpp"
 #include "th04/main/rank.hpp"
 #include "th04/main/item/items.hpp"
 
-void pascal  far nullsub_1(void);
-void pascal near nullfunc_near(void);
-
 void pascal near playfield_fillm_32_0_320_192(void);
 void pascal near playfield_fillm_0_0_384_192__2(void);
 void pascal near playfield_fillm_0_205_384_163(void);
diff --git a/th05_main.asm b/th05_main.asm
index 0b853fecc..d0f4c6f34 100644
--- a/th05_main.asm
+++ b/th05_main.asm
@@ -1950,25 +1950,8 @@ include th04/main/scroll_y_1.asm
 MOTION_UPDATE_DEF 1
 include th03/math/randring_fill.asm
 RANDRING_NEXT_DEF 1
-		nop
-
-; =============== S U B	R O U T	I N E =======================================
-
-public NULLFUNC_NEAR
-nullfunc_near	proc near
-		retn
-nullfunc_near	endp
-		nop
-
-; =============== S U B	R O U T	I N E =======================================
-
-
-public NULLSUB_1
-nullsub_1	proc far
-		retf
-nullsub_1	endp
-		nop
-
+	even
+include th04/main/null.asm
 include th04/main/bullet/pellet_r.asm
 include th04/main/spark_render.asm
 include th04/main/sparks.asm
@@ -13242,7 +13225,7 @@ loc_1603F:
 		les	bx, _std_ip
 		cmp	word ptr es:[bx], 0
 		jnz	short locret_16063
-		setfarfp	_stage_vm, nullsub_1
+		setfarfp	_stage_vm, nullfunc_far
 
 locret_16063:
 		leave
@@ -14945,7 +14928,7 @@ sub_172FF	proc far
 		mov	bp, sp
 		mov	_midboss_invalidate?, offset nullfunc_near
 		mov	_midboss_render, offset nullfunc_near
-		setfarfp	_midboss_update, nullsub_1
+		setfarfp	_midboss_update, nullfunc_far
 		mov	_midboss_hp, 0
 		pop	bp
 		retf