--- a/taskcluster/ci/toolchain/linux.yml
+++ b/taskcluster/ci/toolchain/linux.yml
@@ -293,17 +293,17 @@ linux64-cctools-port:
         max-run-time: 36000
     run:
         using: toolchain-script
         script: build-cctools-port.sh
         resources:
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/cctools.tar.xz
     toolchains:
-        - linux64-clang-3.9
+        - linux64-clang-6
 
 linux64-hfsplus:
     description: "hfsplus toolchain build"
     treeherder:
         kind: build
         platform: toolchains/opt
         symbol: TL(hfs+)
         tier: 1
@@ -313,17 +313,17 @@ linux64-hfsplus:
     run:
         using: toolchain-script
         script: build-hfsplus-linux.sh
         resources:
             - 'build/unix/build-hfsplus/build-hfsplus.sh'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/hfsplus-tools.tar.xz
     toolchains:
-        - linux64-clang-3.9
+        - linux64-clang-6
 
 linux64-libdmg:
     description: "libdmg-hfsplus toolchain build"
     treeherder:
         kind: build
         platform: toolchains/opt
         symbol: TL(libdmg-hfs+)
         tier: 1

--- a/taskcluster/ci/toolchain/macosx.yml
+++ b/taskcluster/ci/toolchain/macosx.yml
@@ -27,17 +27,17 @@ macosx64-clang:
         tooltool-downloads: internal
         resources:
             - 'build/build-clang/build-clang.py'
             - 'build/build-clang/clang-macosx64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/clang.tar.xz
     toolchains:
         - linux64-cctools-port
-        - linux64-clang-3.9
+        - linux64-clang-6
         - linux64-gcc-4.9
 
 macosx64-clang-tidy:
     description: "Clang-tidy build"
     index:
         product: static-analysis
         job-name: macosx64-clang-tidy
     treeherder:
@@ -57,17 +57,17 @@ macosx64-clang-tidy:
         resources:
             - 'build/clang-plugin/**'
             - 'build/build-clang/build-clang.py'
             - 'build/build-clang/clang-tidy-macosx64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/clang-tidy.tar.xz
     toolchains:
         - linux64-cctools-port
-        - linux64-clang-3.9
+        - linux64-clang-6
         - linux64-gcc-4.9
 
 macosx64-cctools-port:
     description: "cctools-port toolchain build"
     treeherder:
         kind: build
         platform: toolchains/opt
         symbol: TM(cctools)
@@ -81,17 +81,17 @@ macosx64-cctools-port:
         using: toolchain-script
         script: build-cctools-port-macosx.sh
         tooltool-downloads: internal
         resources:
             - 'taskcluster/scripts/misc/tooltool-download.sh'
         toolchain-artifact: public/build/cctools.tar.bz2
     toolchains:
         - linux64-cctools-port
-        - linux64-clang-3.9
+        - linux64-clang-6
 
 macosx64-gn:
     description: "gn toolchain build"
     treeherder:
         kind: build
         platform: toolchains/opt
         symbol: TM(gn)
         tier: 1
@@ -105,9 +105,9 @@ macosx64-gn:
         script: build-gn-macosx.sh
         tooltool-downloads: internal
         resources:
             - 'taskcluster/scripts/misc/tooltool-download.sh'
             - 'taskcluster/scripts/misc/build-gn-common.sh'
         toolchain-artifact: public/build/gn.tar.xz
     toolchains:
         - linux64-cctools-port
-        - linux64-clang-3.9
+        - linux64-clang-6