diff --git a/gnu/local.mk b/gnu/local.mk
index 5418d1418d..d0a77c08bb 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1055,7 +1055,6 @@ dist_patch_DATA =						\
   %D%/packages/patches/t1lib-CVE-2011-1552+CVE-2011-1553+CVE-2011-1554.patch		\
   %D%/packages/patches/tar-CVE-2016-6321.patch			\
   %D%/packages/patches/tar-skip-unreliable-tests.patch		\
-  %D%/packages/patches/tcl-mkindex-deterministic.patch		\
   %D%/packages/patches/tclxml-3.2-install.patch			\
   %D%/packages/patches/tcsh-fix-autotest.patch			\
   %D%/packages/patches/tcsh-fix-out-of-bounds-read.patch	\
diff --git a/gnu/packages/patches/tcl-mkindex-deterministic.patch b/gnu/packages/patches/tcl-mkindex-deterministic.patch
deleted file mode 100644
index 2fcef6a4f7..0000000000
--- a/gnu/packages/patches/tcl-mkindex-deterministic.patch
+++ /dev/null
@@ -1,29 +0,0 @@
-This patch ensures that the 'tclIndex' files generated by 'auto_mkindex'
-are sorted in a deterministic fashion.
-
-Fixes a non-determinism issue reported
-at <https://lists.gnu.org/archive/html/guix-devel/2015-10/msg00696.html>.
-
---- tcl8.6.4/library/auto.tcl	2015-02-26 17:57:28.000000000 +0100
-+++ tcl8.6.4/library/auto.tcl	2015-11-13 23:18:34.964831717 +0100
-@@ -207,6 +207,9 @@ proc auto_mkindex {dir args} {
- 	set args *.tcl
-     }
- 
-+    # Keep file names sorted in a determistic order.
-+    set args [lsort -ascii $args]
-+
-     auto_mkindex_parser::init
-     foreach file [glob -- {*}$args] {
- 	try {
-@@ -241,6 +244,10 @@ proc auto_mkindex_old {dir args} {
-     if {![llength $args]} {
- 	set args *.tcl
-     }
-+
-+    # Keep file names sorted in a determistic order.
-+    set args [lsort -ascii $args]
-+
-     foreach file [glob -- {*}$args] {
- 	set f ""
- 	set error [catch {
diff --git a/gnu/packages/tcl.scm b/gnu/packages/tcl.scm
index 8591ff808c..01649ff410 100644
--- a/gnu/packages/tcl.scm
+++ b/gnu/packages/tcl.scm
@@ -38,15 +38,14 @@
 (define-public tcl
   (package
     (name "tcl")
-    (version "8.6.6")
+    (version "8.6.7")
     (source (origin
               (method url-fetch)
               (uri (string-append "mirror://sourceforge/tcl/Tcl/"
                                   version "/tcl" version "-src.tar.gz"))
               (sha256
                (base32
-                "01zypqhy57wvh1ikk28bg733sk5kf4q568pq9v6fvcz4h6bl0rd2"))
-              (patches (search-patches "tcl-mkindex-deterministic.patch"))))
+                "19bb09l55alz4jb38961ikd5116q80s51bjvzqy44ckkwf28ysvw"))))
     (build-system gnu-build-system)
     (arguments
      '(#:phases (alist-cons-before
@@ -137,14 +136,14 @@ X11 GUIs.")
 (define-public tk
   (package
     (name "tk")
-    (version "8.6.6")
+    (version "8.6.7")
     (source (origin
              (method url-fetch)
              (uri (string-append "mirror://sourceforge/tcl/Tcl/"
                                  version "/tk" version "-src.tar.gz"))
              (sha256
               (base32
-               "17diivcfcwdhp4v5zi6j9nkxncccjqkivhp363c4wx5lf4d3fb6n"))
+               "1aipcf6qmbgi15av8yrpp2hx6vdwr684r6739p8cgdzrajiy4786"))
              (patches (search-patches "tk-find-library.patch"))))
     (build-system gnu-build-system)
     (arguments