diff --git a/src/mame/video/xbox_nv2a.cpp b/src/mame/video/xbox_nv2a.cpp
index 9de440a9d87..ea45ff84953 100644
--- a/src/mame/video/xbox_nv2a.cpp
+++ b/src/mame/video/xbox_nv2a.cpp
@@ -502,7 +502,7 @@ void vertex_program_simulator::decode_instruction(int address)
 int vertex_program_simulator::step()
 {
 	int p1, p2;
-	float tmp[3 * 4];
+	float tmp[3 * 4] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
 	float tmpv[4] = { 0, 0, 0, 0};
 	float tmps[4] = { 0, 0, 0, 0};
 	instruction::decoded *d;