diff --git a/Source/Core/Core/Src/HW/DSPHLE/UCodes/UCode_AX_Voice.h b/Source/Core/Core/Src/HW/DSPHLE/UCodes/UCode_AX_Voice.h
index 7bf060b0d4..64a01ca8fe 100644
--- a/Source/Core/Core/Src/HW/DSPHLE/UCodes/UCode_AX_Voice.h
+++ b/Source/Core/Core/Src/HW/DSPHLE/UCodes/UCode_AX_Voice.h
@@ -30,6 +30,8 @@
 #include "UCode_AXStructs.h"
 #include "../../DSP.h"
 
+#include <functional>
+
 #ifdef AX_GC
 # define PB_TYPE AXPB
 # define SAMPLES_PER_FRAME 32