diff --git a/pcsx2/GS/Renderers/Metal/GSDeviceMTL.mm b/pcsx2/GS/Renderers/Metal/GSDeviceMTL.mm
index 7037ad4810a96..3e811c8f78ce4 100644
--- a/pcsx2/GS/Renderers/Metal/GSDeviceMTL.mm
+++ b/pcsx2/GS/Renderers/Metal/GSDeviceMTL.mm
@@ -1388,7 +1388,7 @@ static GSMTLExpandType ConvertVSExpand(GSHWDrawConfig::VSExpand generic)
 		setFnConstantI(m_fn_constants, pssel.blend_c,            GSMTLConstantIndex_PS_BLEND_C);
 		setFnConstantI(m_fn_constants, pssel.blend_d,            GSMTLConstantIndex_PS_BLEND_D);
 		setFnConstantI(m_fn_constants, pssel.blend_hw,           GSMTLConstantIndex_PS_BLEND_HW);
-		setFnConstantI(m_fn_constants, pssel.a_masked,           GSMTLConstantIndex_PS_A_MASKED);
+		setFnConstantB(m_fn_constants, pssel.a_masked,           GSMTLConstantIndex_PS_A_MASKED);
 		setFnConstantB(m_fn_constants, pssel.hdr,                GSMTLConstantIndex_PS_HDR);
 		setFnConstantB(m_fn_constants, pssel.colclip,            GSMTLConstantIndex_PS_COLCLIP);
 		setFnConstantI(m_fn_constants, pssel.blend_mix,          GSMTLConstantIndex_PS_BLEND_MIX);