diff --git a/infra/config/global/cr-buildbucket.cfg b/infra/config/global/cr-buildbucket.cfg
index 88b541b406..515e804f71 100644
--- a/infra/config/global/cr-buildbucket.cfg
+++ b/infra/config/global/cr-buildbucket.cfg
@@ -104,25 +104,25 @@ buckets {
     # Linux: test combinations of {clang}x{release,debug}x{x86,x64}
     builders {
       name: "linux-clang-dbg-x64"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "debug"
       mixins: "x64"
     }
     builders {
       name: "linux-clang-dbg-x86"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "debug"
       mixins: "x86"
     }
     builders {
       name: "linux-clang-rel-x64"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "release"
       mixins: "x64"
     }
     builders {
       name: "linux-clang-rel-x86"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "release"
       mixins: "x86"
     }
@@ -212,7 +212,7 @@ buckets: {
 
     builders {
       name: "presubmit"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       recipe {
         name: "run_presubmit"
         properties: "repo_name:dawn"
@@ -227,28 +227,28 @@ buckets: {
     # CI Mirror only
     builders {
       name: "linux-clang-dbg-x64"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "debug"
       mixins: "x64"
     }
     # Actually on the CQ
     builders {
       name: "linux-clang-dbg-x86"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "debug"
       mixins: "x86"
     }
     # Actually on the CQ
     builders {
       name: "linux-clang-rel-x64"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "release"
       mixins: "x64"
     }
     # Actually on the CQ
     builders {
       name: "linux-clang-rel-x86"
-      dimensions: "os:Ubuntu"
+      dimensions: "os:Ubuntu-16.04"
       mixins: "release"
       mixins: "x86"
     }