diff --git a/pkgs/development/interpreters/tcl/8.5.nix b/pkgs/development/interpreters/tcl/8.5.nix
new file mode 100644
index 000000000000..193ff4f93769
--- /dev/null
+++ b/pkgs/development/interpreters/tcl/8.5.nix
@@ -0,0 +1,11 @@
+{ callPackage, fetchurl, ... } @ args:
+
+callPackage ./generic.nix (args // rec {
+  release = "8.5";
+  version = "${release}.18";
+
+  src = fetchurl {
+    url = "mirror://sourceforge/tcl/tcl${version}-src.tar.gz";
+    sha256 = "1jfkqp2fr0xh6xvaqx134hkfa5kh7agaqbxm6lhjbpvvc1xfaaq3";
+  };
+})
diff --git a/pkgs/development/interpreters/tcl/8.6.nix b/pkgs/development/interpreters/tcl/8.6.nix
new file mode 100644
index 000000000000..fd88c8e87166
--- /dev/null
+++ b/pkgs/development/interpreters/tcl/8.6.nix
@@ -0,0 +1,11 @@
+{ callPackage, fetchurl, ... } @ args:
+
+callPackage ./generic.nix (args // rec {
+  release = "8.6";
+  version = "${release}.4";
+
+  src = fetchurl {
+    url = "mirror://sourceforge/tcl/tcl${version}-src.tar.gz";
+    sha256 = "13cwa4bc85ylf5gfj9vk182lvgy60qni3f7gbxghq78wk16djvly";
+  };
+})
diff --git a/pkgs/development/interpreters/tcl/default.nix b/pkgs/development/interpreters/tcl/generic.nix
similarity index 68%
rename from pkgs/development/interpreters/tcl/default.nix
rename to pkgs/development/interpreters/tcl/generic.nix
index aa3836399ba5..8b5722c79c8d 100644
--- a/pkgs/development/interpreters/tcl/default.nix
+++ b/pkgs/development/interpreters/tcl/generic.nix
@@ -1,15 +1,14 @@
-{ stdenv, fetchurl }:
-let
-  release = "8.6";
-in
+{ stdenv, fetchurl
+
+# Version specific stuff
+, release, version, src
+, ...
+}:
+
 stdenv.mkDerivation rec {
   name = "tcl-${version}";
-  version = "${release}.4";
 
-  src = fetchurl {
-    url = "mirror://sourceforge/tcl/tcl${version}-src.tar.gz";
-    sha256 = "13cwa4bc85ylf5gfj9vk182lvgy60qni3f7gbxghq78wk16djvly";
-  };
+  inherit src;
 
   preConfigure = "cd unix";
 
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index a34e16b71bc0..6fb12b7526a2 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -4791,7 +4791,9 @@ let
 
   sysPerl = callPackage ../development/interpreters/perl/sys-perl { };
 
-  tcl = callPackage ../development/interpreters/tcl { };
+  tcl = tcl-8_6;
+  tcl-8_5 = callPackage ../development/interpreters/tcl/8.5.nix { };
+  tcl-8_6 = callPackage ../development/interpreters/tcl/8.6.nix { };
 
   xulrunner = callPackage ../development/interpreters/xulrunner {
     inherit (gnome) libIDL;