diff --git a/CHANGES b/CHANGES
index 5c1599a20..afb21e008 100644
--- a/CHANGES
+++ b/CHANGES
@@ -33,6 +33,7 @@ Emulation fixes:
  - GBA: Improve timing when not booting from BIOS
  - GBA: Fix expected entry point for multiboot ELFs (fixes mgba.io/i/2450)
  - GBA: Fix booting multiboot ROMs with no JOY entrypoint
+ - GBA: Fix 1 MiB ROM mirroring to only mirror 4 times
  - GBA Audio: Adjust PSG sampling rate with SOUNDBIAS
  - GBA Audio: Sample FIFOs at SOUNDBIAS-set frequency
  - GBA BIOS: Work around IRQ handling hiccup in Mario & Luigi (fixes mgba.io/i/1059)
diff --git a/src/gba/gba.c b/src/gba/gba.c
index a6df59f4c..70da8e345 100644
--- a/src/gba/gba.c
+++ b/src/gba/gba.c
@@ -364,7 +364,6 @@ bool GBALoadNull(struct GBA* gba) {
 	gba->yankedRomSize = 0;
 	gba->memory.romSize = SIZE_CART0;
 	gba->memory.romMask = SIZE_CART0 - 1;
-	gba->memory.mirroring = false;
 	gba->romCrc32 = 0;
 
 	if (gba->cpu) {
@@ -419,6 +418,19 @@ bool GBALoadROM(struct GBA* gba, struct VFile* vf) {
 			gba->memory.romSize = SIZE_CART0;
 		}
 		gba->pristineRomSize = SIZE_CART0;
+	} else if (gba->pristineRomSize == 0x00100000) {
+		// 1 MiB ROMs (e.g. Classic NES) all appear as 4x mirrored, but not more
+		gba->isPristine = false;
+		gba->memory.romSize = 0x00400000;
+#ifdef FIXED_ROM_BUFFER
+		gba->memory.rom = romBuffer;
+#else
+		gba->memory.rom = anonymousMemoryMap(SIZE_CART0);
+#endif
+		vf->read(vf, gba->memory.rom, gba->pristineRomSize);
+		memcpy(&gba->memory.rom[0x40000], gba->memory.rom, 0x00100000);
+		memcpy(&gba->memory.rom[0x80000], gba->memory.rom, 0x00100000);
+		memcpy(&gba->memory.rom[0xC0000], gba->memory.rom, 0x00100000);
 	} else {
 		gba->memory.rom = vf->map(vf, gba->pristineRomSize, MAP_READ);
 		gba->memory.romSize = gba->pristineRomSize;
@@ -430,8 +442,7 @@ bool GBALoadROM(struct GBA* gba, struct VFile* vf) {
 	}
 	gba->yankedRomSize = 0;
 	gba->memory.romMask = toPow2(gba->memory.romSize) - 1;
-	gba->memory.mirroring = false;
-	gba->romCrc32 = doCrc32(gba->memory.rom, gba->memory.romSize);
+	gba->romCrc32 = doCrc32(gba->memory.rom, gba->pristineRomSize);
 	if (popcount32(gba->memory.romSize) != 1) {
 		// This ROM is either a bad dump or homebrew. Emulate flash cart behavior.
 #ifndef FIXED_ROM_BUFFER
diff --git a/src/gba/memory.c b/src/gba/memory.c
index 1878e7bb2..c9a1f59dd 100644
--- a/src/gba/memory.c
+++ b/src/gba/memory.c
@@ -83,7 +83,6 @@ void GBAMemoryInit(struct GBA* gba) {
 	cpu->memory.activeNonseqCycles32 = 0;
 	cpu->memory.activeNonseqCycles16 = 0;
 	gba->memory.biosPrefetch = 0;
-	gba->memory.mirroring = false;
 
 	gba->memory.agbPrintProtect = 0;
 	memset(&gba->memory.agbPrintCtx, 0, sizeof(gba->memory.agbPrintCtx));
@@ -277,9 +276,6 @@ static void GBASetActiveRegion(struct ARMCore* cpu, uint32_t address) {
 		if (newRegion < REGION_CART0 || (address & (SIZE_CART0 - 1)) < memory->romSize) {
 			return;
 		}
-		if (memory->mirroring && (address & memory->romMask) < memory->romSize) {
-			return;
-		}
 	}
 
 	if (memory->activeRegion == REGION_BIOS) {
@@ -411,8 +407,6 @@ static void GBASetActiveRegion(struct ARMCore* cpu, uint32_t address) {
 	wait += waitstatesRegion[address >> BASE_OFFSET]; \
 	if ((address & (SIZE_CART0 - 1)) < memory->romSize) { \
 		LOAD_32(value, address & (SIZE_CART0 - 4), memory->rom); \
-	} else if (memory->mirroring && (address & memory->romMask) < memory->romSize) { \
-		LOAD_32(value, address & memory->romMask & -4, memory->rom); \
 	} else if (memory->vfame.cartType) { \
 		value = GBAVFameGetPatternValue(address, 32); \
 	} else { \
@@ -578,8 +572,6 @@ uint32_t GBALoad16(struct ARMCore* cpu, uint32_t address, int* cycleCounter) {
 		wait = memory->waitstatesNonseq16[address >> BASE_OFFSET];
 		if ((address & (SIZE_CART0 - 1)) < memory->romSize) {
 			LOAD_16(value, address & (SIZE_CART0 - 2), memory->rom);
-		} else if (memory->mirroring && (address & memory->romMask) < memory->romSize) {
-			LOAD_16(value, address & memory->romMask, memory->rom);
 		} else if (memory->vfame.cartType) {
 			value = GBAVFameGetPatternValue(address, 16);
 		} else if ((address & (SIZE_CART0 - 1)) >= AGB_PRINT_BASE) {
@@ -605,8 +597,6 @@ uint32_t GBALoad16(struct ARMCore* cpu, uint32_t address, int* cycleCounter) {
 			value = GBACartEReaderRead(&memory->ereader, address);
 		} else if ((address & (SIZE_CART0 - 1)) < memory->romSize) {
 			LOAD_16(value, address & (SIZE_CART0 - 2), memory->rom);
-		} else if (memory->mirroring && (address & memory->romMask) < memory->romSize) {
-			LOAD_16(value, address & memory->romMask, memory->rom);
 		} else if (memory->vfame.cartType) {
 			value = GBAVFameGetPatternValue(address, 16);
 		} else {
@@ -698,8 +688,6 @@ uint32_t GBALoad8(struct ARMCore* cpu, uint32_t address, int* cycleCounter) {
 		wait = memory->waitstatesNonseq16[address >> BASE_OFFSET];
 		if ((address & (SIZE_CART0 - 1)) < memory->romSize) {
 			value = ((uint8_t*) memory->rom)[address & (SIZE_CART0 - 1)];
-		} else if (memory->mirroring && (address & memory->romMask) < memory->romSize) {
-			value = ((uint8_t*) memory->rom)[address & memory->romMask];
 		} else if (memory->vfame.cartType) {
 			value = GBAVFameGetPatternValue(address, 8);
 		} else {
diff --git a/src/gba/overrides.c b/src/gba/overrides.c
index 823957d5c..a0593a90e 100644
--- a/src/gba/overrides.c
+++ b/src/gba/overrides.c
@@ -229,7 +229,6 @@ bool GBAOverrideFind(const struct Configuration* config, struct GBACartridgeOver
 	if (!found && override->id[0] == 'F') {
 		// Classic NES Series
 		override->savetype = SAVEDATA_EEPROM;
-		override->mirroring = true;
 		found = true;
 	}
 
@@ -377,10 +376,6 @@ void GBAOverrideApply(struct GBA* gba, const struct GBACartridgeOverride* overri
 			gba->idleOptimization = IDLE_LOOP_REMOVE;
 		}
 	}
-
-	if (override->mirroring) {
-		gba->memory.mirroring = true;
-	}
 }
 
 void GBAOverrideApplyDefaults(struct GBA* gba, const struct Configuration* overrides) {