diff --git a/include/mgba/internal/gba/renderers/video-software.h b/include/mgba/internal/gba/renderers/video-software.h
index 59c2a7ce8..514dc3593 100644
--- a/include/mgba/internal/gba/renderers/video-software.h
+++ b/include/mgba/internal/gba/renderers/video-software.h
@@ -139,9 +139,9 @@ struct GBAVideoSoftwareRenderer {
 	int16_t objOffsetY;
 
 	uint32_t scanlineDirty[5];
-	uint16_t nextIo[REG_SOUND1CNT_LO];
+	uint16_t nextIo[REG_SOUND1CNT_LO >> 1];
 	struct ScanlineCache {
-		uint16_t io[REG_SOUND1CNT_LO];
+		uint16_t io[REG_SOUND1CNT_LO >> 1];
 		int32_t scale[2][2];
 	} cache[GBA_VIDEO_VERTICAL_PIXELS];
 	int nextY;