diff --git a/CHANGES b/CHANGES
index 107e6d0e6..017aaf589 100644
--- a/CHANGES
+++ b/CHANGES
@@ -30,6 +30,7 @@ Bugfixes:
  - GBA: Handle out-of-bounds I/O access
  - GBA: Fix bounds-checking on EEPROM access
  - ARM7: Make illegal instruction decoding consistent between ARM and Thumb
+ - GBA BIOS: Initialize a variable that may be uninitialized in very rare cases
 Misc:
  - Qt: Show multiplayer numbers in window title
  - Qt: Solar sensor can have shortcuts set
diff --git a/src/gba/bios.c b/src/gba/bios.c
index c68119550..0b588ac9b 100644
--- a/src/gba/bios.c
+++ b/src/gba/bios.c
@@ -331,7 +331,7 @@ static void _unLz77(struct GBA* gba, int width) {
 	uint32_t disp;
 	int bytes;
 	int byte;
-	int halfword;
+	int halfword = 0;
 	while (remaining > 0) {
 		if (blocksRemaining) {
 			if (blockheader & 0x80) {