diff --git a/vispy/glsl/math/double.glsl b/vispy/glsl/math/double.glsl
index 855d5d337a..c13347d631 100644
--- a/vispy/glsl/math/double.glsl
+++ b/vispy/glsl/math/double.glsl
@@ -5,7 +5,7 @@
 /*
   This shader program emulates double-precision variables using a vec2 instead
   of single-precision floats. Any function starting with double_* operates on
-  these variables. See http://www.thasler.org/blog/?p=93.
+  these variables. See https://blog.cyclemap.link/2011-06-09-glsl-part2-emu/.
 
   NOTE: Some NVIDIA cards optimize the double-precision code away. Results are
   therefore hardware dependent.