diff --git a/contrib/lua/hooks.lua.in b/contrib/lua/hooks.lua.in
index 695c8bf56..d3537cf56 100644
--- a/contrib/lua/hooks.lua.in
+++ b/contrib/lua/hooks.lua.in
@@ -156,7 +156,7 @@ function hx (c)
 end
 
 function char2hex (c)
-    return '%'..hx (string.byte (c) / 16)..hx (math.mod(string.byte (c), 16))
+    return '%'..hx (string.byte (c) / 16)..hx (math.fmod(string.byte (c), 16))
 end
 
 function escape (str)