diff --git a/shared/rd-rend2/tr_weather.cpp b/shared/rd-rend2/tr_weather.cpp
index 36b8ed65ea..f7a7c0e17a 100644
--- a/shared/rd-rend2/tr_weather.cpp
+++ b/shared/rd-rend2/tr_weather.cpp
@@ -1149,6 +1149,11 @@ void RB_SurfaceWeather( srfWeather_t *surf )
 			{
 				chunkIndex  = (int(centerZoneOffsetX + numMinZonesX) + x + 1) % 3;
 				chunkIndex += (int(centerZoneOffsetY + numMinZonesY) + y + 1) % 3 * 3;
+
+				if (chunkIndex < 0) {
+					chunkIndex += 9;
+				}
+
 				VectorSet2(
 					zoneOffsets[chunkIndex],
 					x,