--- a/taskcluster/ci/test/tests.yml
+++ b/taskcluster/ci/test/tests.yml
@@ -40,20 +40,17 @@ cppunit:
 crashtest:
     description: "Crashtest run"
     suite: reftest/crashtest
     treeherder-symbol: tc-R(C)
     instance-size:
         by-test-platform:
             android.*: xlarge
             default: default
-    docker-image:
-        by-test-platform:
-            android.*: {'in-tree': 'desktop-test'}
-            default: {"in-tree": 'desktop1604-test'}
+    docker-image: {"in-tree": "desktop1604-test"}
     chunks:
         by-test-platform:
             android-4.3-arm7-api-15/debug: 10
             android.*: 4
             default: 1
     e10s:
         by-test-platform:
             windows.*: false # Bug 1304435
@@ -240,20 +237,17 @@ marionette:
     max-run-time:
         by-test-platform:
             android.*: 3600
             default: 5400
     instance-size:
         by-test-platform:
             android.*: xlarge
             default: default
-    docker-image:
-        by-test-platform:
-            android.*: {'in-tree': 'desktop-test'}
-            default: {"in-tree": 'desktop1604-test'}
+    docker-image: {"in-tree": "desktop1604-test"}
     tier:
         by-test-platform:
             android.*: 3
             default: default
     chunks:
         by-test-platform:
             android.*: 10
             default: 1
@@ -641,20 +635,17 @@ mochitest-media:
     instance-size:
         by-test-platform:
             android.*: xlarge
             default: large
     chunks:
         by-test-platform:
             android.*: 3
             default: 1
-    docker-image:
-        by-test-platform:
-            android.*: {'in-tree': 'desktop-test'}
-            default: {"in-tree": 'desktop1604-test'}
+    docker-image: {"in-tree": "desktop1604-test"}
     mozharness:
         by-test-platform:
             android.*:
                 script: android_emulator_unittest.py
                 no-read-buildbot-config: true
                 config:
                     - android/androidarm_4_3.py
                     - remove_executables.py
@@ -789,20 +780,17 @@ mochitest-style:
                     - remove_executables.py
         extra-options:
             - --mochitest-suite=mochitest-style
 
 reftest:
     description: "Reftest run"
     suite: reftest/reftest
     treeherder-symbol: tc-R(R)
-    docker-image:
-        by-test-platform:
-            android.*: {'in-tree': 'desktop-test'}
-            default: {"in-tree": 'desktop1604-test'}
+    docker-image: {"in-tree": "desktop1604-test"}
     instance-size:
         by-test-platform:
             android.*: xlarge
             default: default
     chunks:
         by-test-platform:
             android-4.3-arm7-api-15/debug: 48
             android.*: 16