diff --git a/src/r_things.cpp b/src/r_things.cpp
index d83e61f27..3c4385f29 100644
--- a/src/r_things.cpp
+++ b/src/r_things.cpp
@@ -2538,8 +2538,8 @@ static void R_ProjectSprite(mobj_t *thing)
 		// diminished light
 		lindex = FixedMul(xscale, LIGHTRESOLUTIONFIX)>>(LIGHTSCALESHIFT);
 
-		if (lindex >= MAXLIGHTSCALE)
-			lindex = MAXLIGHTSCALE-1;
+		// Mitigate against negative xscale and arithmetic overflow
+		lindex = std::clamp(lindex, 0, MAXLIGHTSCALE - 1);
 
 		if (vis->cut & SC_SEMIBRIGHT)
 			lindex = (MAXLIGHTSCALE/2) + (lindex >> 1);