diff --git a/pyopencl/clrandom.py b/pyopencl/clrandom.py
index ab4805b20e85b1ed30dc88c8302573da61aa310d..7710bc60e99e026e070b6e09714649847821e627 100644
--- a/pyopencl/clrandom.py
+++ b/pyopencl/clrandom.py
@@ -124,7 +124,7 @@ class RanluxGenerator(object):
               if (idx+2 < out_size)
                 output[idx+2] = tail_ran.z;
               if (idx+3 < out_size)
-                output[idx+2] = tail_ran.w;
+                output[idx+3] = tail_ran.w;
 
               ranluxcl_upload_seed(&ranluxclstate, ranluxcltab);
             }