diff --git a/src/noise.cpp b/src/noise.cpp
index 46067e09d..ee6ddf871 100644
--- a/src/noise.cpp
+++ b/src/noise.cpp
@@ -167,6 +167,7 @@ float noise2d(int x, int y, s32 seed)
 {
 	unsigned int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y
 			+ NOISE_MAGIC_SEED * seed) & 0x7fffffff;
+	// Right bit shift on an unsigned type zero-fills.
 	n = (n >> 13) ^ n;
 	n = (n * (n * n * 60493 + 19990303) + 1376312589) & 0x7fffffff;
 	return 1.f - (float)(int)n / 0x40000000;