diff --git a/Source/lighting.cpp b/Source/lighting.cpp
index da1743f16..e84641740 100644
--- a/Source/lighting.cpp
+++ b/Source/lighting.cpp
@@ -1173,7 +1173,7 @@ void InitVision()
 
 int AddVision(int x, int y, int r, BOOL mine)
 {
-	int vid; // BUGFIX: if numvision >= MAXVISION behavior is undefined
+	int vid = -1; // BUGFIX: if numvision >= MAXVISION behavior is undefined
 
 	if (numvision < MAXVISION) {
 		VisionList[numvision]._lx = x;