diff --git a/pkgs/development/interpreters/tcl/8.6.nix b/pkgs/development/interpreters/tcl/8.6.nix
index 0edd47e83d6c..9da653b2f761 100644
--- a/pkgs/development/interpreters/tcl/8.6.nix
+++ b/pkgs/development/interpreters/tcl/8.6.nix
@@ -2,12 +2,12 @@
 
 callPackage ./generic.nix (args // rec {
   release = "8.6";
-  version = "${release}.13";
+  version = "${release}.15";
 
   # Note: when updating, the hash in pkgs/development/libraries/tk/8.6.nix must also be updated!
 
   src = fetchurl {
     url = "mirror://sourceforge/tcl/tcl${version}-src.tar.gz";
-    sha256 = "sha256-Q6H650EvYf8R3iz9BdKM/Dpzdi81SkF8YjcKVOLK8GY=";
+    sha256 = "sha256-hh4Vl1Py4vvW7BSEEDcVsL5WvjNXUiuFjTy7X4k//vE=";
   };
 })