diff --git a/include/mgba/internal/gb/io.h b/include/mgba/internal/gb/io.h
index 44d83290c..ada06dcb1 100644
--- a/include/mgba/internal/gb/io.h
+++ b/include/mgba/internal/gb/io.h
@@ -100,9 +100,10 @@ enum GBIORegisters {
 	GB_REG_OCPD = 0x6B,
 	GB_REG_OPRI = 0x6C,
 	GB_REG_SVBK = 0x70,
-	GB_REG_UNK72 = 0x72,
-	GB_REG_UNK73 = 0x73,
-	GB_REG_UNK74 = 0x74,
+	GB_REG_PSM = 0x71,
+	GB_REG_PSWX = 0x72,
+	GB_REG_PSWY = 0x73,
+	GB_REG_PSW = 0x74,
 	GB_REG_UNK75 = 0x75,
 	GB_REG_PCM12 = 0x76,
 	GB_REG_PCM34 = 0x77,
diff --git a/src/gb/io.c b/src/gb/io.c
index 74ce4caee..affa99a51 100644
--- a/src/gb/io.c
+++ b/src/gb/io.c
@@ -687,8 +687,10 @@ uint8_t GBIORead(struct GB* gb, unsigned address) {
 	case GB_REG_OCPS:
 	case GB_REG_OCPD:
 	case GB_REG_SVBK:
-	case GB_REG_UNK72:
-	case GB_REG_UNK73:
+	case GB_REG_PSM:
+	case GB_REG_PSWX:
+	case GB_REG_PSWY:
+	case GB_REG_PSW:
 	case GB_REG_UNK75:
 		// Handled transparently by the registers
 		if (gb->model < GB_MODEL_CGB) {