diff --git a/src/emu/cpu/rsp/rspcp2d.c b/src/emu/cpu/rsp/rspcp2d.c
index 8f8d603a0d5..cc33779e5f4 100644
--- a/src/emu/cpu/rsp/rspcp2d.c
+++ b/src/emu/cpu/rsp/rspcp2d.c
@@ -1368,7 +1368,7 @@ void rsp_cop2_drc::vmulf()
 		if (s1 == -32768 && s2 == -32768)
 		{
 			// overflow
-			ACCUM(i) = 0x0000800080000000L;
+			ACCUM(i) = S64(0x0000800080000000);
 			m_vres[i] = 0x7fff;
 		}
 		else