diff --git a/include/mgba/internal/gba/serialize.h b/include/mgba/internal/gba/serialize.h
index 4f24198dd..691a6a711 100644
--- a/include/mgba/internal/gba/serialize.h
+++ b/include/mgba/internal/gba/serialize.h
@@ -194,6 +194,7 @@ mLOG_DECLARE_CATEGORY(GBA_STATE);
  * 0x00318 - 0x0031B: Last prefetched program counter
  * 0x0031C - 0x0031F: Miscellaneous flags
  *  | bit 0: Is CPU halted?
+ *  | bit 1: POSTFLG
  * 0x00320 - 0x003FF: Reserved (leave zero)
  * 0x00400 - 0x007FF: I/O memory
  * 0x00800 - 0x00BFF: Palette
@@ -224,6 +225,7 @@ DECL_BIT(GBASerializedSavedataFlags, DustSettling, 5);
 
 DECL_BITFIELD(GBASerializedMiscFlags, uint32_t);
 DECL_BIT(GBASerializedMiscFlags, Halted, 0);
+DECL_BIT(GBASerializedMiscFlags, POSTFLG, 1);
 
 struct GBASerializedState {
 	uint32_t versionMagic;
diff --git a/src/gba/serialize.c b/src/gba/serialize.c
index 5917fa5f1..9360fcf8e 100644
--- a/src/gba/serialize.c
+++ b/src/gba/serialize.c
@@ -61,6 +61,7 @@ void GBASerialize(struct GBA* gba, struct GBASerializedState* state) {
 
 	GBASerializedMiscFlags miscFlags = 0;
 	miscFlags = GBASerializedMiscFlagsSetHalted(miscFlags, gba->cpu->halted);
+	miscFlags = GBASerializedMiscFlagsSetPOSTFLG(miscFlags, gba->memory.io[REG_POSTFLG >> 1] & 1);
 	STORE_32(miscFlags, 0, &state->miscFlags);
 
 	GBAMemorySerialize(&gba->memory, state);
@@ -175,6 +176,7 @@ bool GBADeserialize(struct GBA* gba, const struct GBASerializedState* state) {
 	GBASerializedMiscFlags miscFlags = 0;
 	LOAD_32(miscFlags, 0, &state->miscFlags);
 	gba->cpu->halted = GBASerializedMiscFlagsGetHalted(miscFlags);
+	gba->memory.io[REG_POSTFLG >> 1] = GBASerializedMiscFlagsGetPOSTFLG(miscFlags);
 
 	GBAVideoDeserialize(&gba->video, state);
 	GBAMemoryDeserialize(&gba->memory, state);