diff --git a/Makefile b/Makefile
index 754ecebe360c..0ae0ccd325de 100644
--- a/Makefile
+++ b/Makefile
@@ -123,7 +123,7 @@ else
   MODERNCC := $(PREFIX)gcc
   PATH_MODERNCC := PATH="$(PATH)" $(MODERNCC)
   CC1 := $(shell $(PATH_MODERNCC) --print-prog-name=cc1) -quiet
-  override CFLAGS += -mthumb -mthumb-interwork -O$(O_LEVEL) -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast
+  override CFLAGS += -mthumb -mthumb-interwork -O$(O_LEVEL) -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-strict-aliasing -Wno-pointer-to-int-cast
   LIBPATH := -L "$(dir $(shell $(PATH_MODERNCC) -mthumb -print-file-name=libgcc.a))" -L "$(dir $(shell $(PATH_MODERNCC) -mthumb -print-file-name=libnosys.a))" -L "$(dir $(shell $(PATH_MODERNCC) -mthumb -print-file-name=libc.a))"
   LIB := $(LIBPATH) -lc -lnosys -lgcc -L../../libagbsyscall -lagbsyscall
 endif
@@ -293,7 +293,9 @@ $(C_BUILDDIR)/record_mixing.o: CFLAGS += -ffreestanding
 $(C_BUILDDIR)/librfu_intr.o: CC1 := $(TOOLS_DIR)/agbcc/bin/agbcc_arm$(EXE)
 $(C_BUILDDIR)/librfu_intr.o: CFLAGS := -O2 -mthumb-interwork -quiet
 else
-$(C_BUILDDIR)/librfu_intr.o: CFLAGS := -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -Wno-pointer-to-int-cast
+$(C_BUILDDIR)/m4a.o: CFLAGS += -fno-toplevel-reorder
+$(C_BUILDDIR)/librfu_intr.o: CFLAGS := -mthumb-interwork -O2 -mabi=apcs-gnu -mtune=arm7tdmi -march=armv4t -fno-toplevel-reorder -fno-strict-aliasing -Wno-pointer-to-int-cast
+$(C_BUILDDIR)/agb_flash.o: CFLAGS += -fno-toplevel-reorder
 $(C_BUILDDIR)/berry_crush.o: override CFLAGS += -Wno-address-of-packed-member
 endif
 
diff --git a/include/gba/types.h b/include/gba/types.h
index 2e92bbe86e56..1308846a99e5 100644
--- a/include/gba/types.h
+++ b/include/gba/types.h
@@ -2,6 +2,7 @@
 #define GUARD_GBA_TYPES_H
 
 #include <stdint.h>
+#include "gba/defines.h"
 
 typedef uint8_t   u8;
 typedef uint16_t u16;
@@ -69,7 +70,7 @@ struct OamData
              u16 priority:2;    // 0x400, 0x800 -> 0xC00
              u16 paletteNum:4;
     /*0x06*/ u16 affineParam;
-};
+} ALIGNED(4); // Modern compilers will use wrong align-of sometimes.
 
 #define ST_OAM_HFLIP     0x08
 #define ST_OAM_VFLIP     0x10
diff --git a/include/global.h b/include/global.h
index bdfc426fb93c..93b13872aac6 100644
--- a/include/global.h
+++ b/include/global.h
@@ -17,11 +17,12 @@
 #include "constants/easy_chat.h"
 #include "constants/trainer_hill.h"
 
-// Prevent cross-jump optimization.
-#define BLOCK_CROSS_JUMP asm("");
-
-// to help in decompiling
+// Unified Thumb/ARM asm. Modern (Clang): no .syntax divided — Clang rejects it. Legacy agbcc output still expects divided after the block.
+#if MODERN
+#define asm_unified(x) asm(".syntax unified\n" x)
+#else
 #define asm_unified(x) asm(".syntax unified\n" x "\n.syntax divided")
+#endif
 #define NAKED __attribute__((naked))
 
 #if MODERN
diff --git a/src/multiboot.c b/src/multiboot.c
index 15b062ed65ee..f452616521d6 100644
--- a/src/multiboot.c
+++ b/src/multiboot.c
@@ -441,16 +441,16 @@ static void MultiBootWaitCycles(u32 cycles)
 {
     asm_unified("\
     mov  r2, pc\n\
-    lsrs r2, 24\n\
-    movs r1, 12\n\
-    cmp  r2, 2\n\
+    lsrs r2, r2, #24\n\
+    movs r1, #12\n\
+    cmp  r2, #2\n\
     beq  MultiBootWaitCyclesLoop\n\
-    movs r1, 13\n\
-    cmp  r2, 8\n\
+    movs r1, #13\n\
+    cmp  r2, #8\n\
     beq  MultiBootWaitCyclesLoop\n\
-    movs r1, 4\n\
+    movs r1, #4\n\
 MultiBootWaitCyclesLoop:\n\
-    subs r0, r1\n\
+    subs r0, r0, r1\n\
     bgt  MultiBootWaitCyclesLoop\n\
     bx   lr\n");
 }