diff --git a/src/classicnoise3D.glsl b/src/classicnoise3D.glsl
index c252e79..7ed6d79 100644
--- a/src/classicnoise3D.glsl
+++ b/src/classicnoise3D.glsl
@@ -2,7 +2,7 @@
 // GLSL textureless classic 3D noise "cnoise",
 // with an RSL-style periodic variant "pnoise".
 // Author:  Stefan Gustavson (stefan.gustavson@liu.se)
-// Version: 2011-08-22
+// Version: 2011-10-11
 //
 // Many thanks to Ian McEwan of Ashima Arts for the
 // ideas for permutation and gradient selection.
@@ -12,7 +12,7 @@
 // https://github.com/ashima/webgl-noise
 //
 
-vec4 mod289(vec4 x)
+vec3 mod289(vec3 x)
 {
   return x - floor(x * (1.0 / 289.0)) * 289.0;
 }