diff --git a/etc/taskcluster/decision_task.py b/etc/taskcluster/decision_task.py
index 0d3a4fbe174..951cebe7afa 100644
--- a/etc/taskcluster/decision_task.py
+++ b/etc/taskcluster/decision_task.py
@@ -186,7 +186,7 @@ def linux_tidy_unit():
             ./etc/ci/lockfile_changed.sh
             ./etc/ci/check_no_panic.sh
         """)
-        .find_or_create("linux_unit." + CONFIG.task_id())
+        .find_or_create("linux_unit." + CONFIG.tree_hash())
     )
 
 
@@ -216,12 +216,12 @@ def linux_docs_check():
             ./mach check
         """)
         .with_artifacts("/repo/target/doc/docs.bundle")
-        .find_or_create("docs." + CONFIG.task_id())
+        .find_or_create("docs." + CONFIG.tree_hash())
     )
 
 
 def upload_docs():
-    docs_build_task_id = decisionlib.Task.find("docs." + CONFIG.task_id())
+    docs_build_task_id = decisionlib.Task.find("docs." + CONFIG.tree_hash())
     return (
         linux_task("Upload docs to GitHub Pages")
         .with_treeherder("Linux x64", "DocUpload")
@@ -257,7 +257,7 @@ def macos_unit():
             ./mach package --dev
             ./etc/ci/lockfile_changed.sh
         """)
-        .find_or_create("macos_unit." + CONFIG.task_id())
+        .find_or_create("macos_unit." + CONFIG.tree_hash())
     )
 
 
@@ -302,7 +302,7 @@ def windows_arm64():
             "python mach package --dev --target aarch64-uwp-windows-msvc --uwp=arm64",
         )
         .with_artifacts(appx_artifact(debug=True))
-        .find_or_create("build.windows_uwp_arm64_dev." + CONFIG.task_id())
+        .find_or_create("build.windows_uwp_arm64_dev." + CONFIG.tree_hash())
     )
 
 
@@ -318,7 +318,7 @@ def windows_uwp_x64():
             "python mach test-tidy --force-cpp --no-wpt",
         )
         .with_artifacts(appx_artifact(debug=True))
-        .find_or_create("build.windows_uwp_x64_dev." + CONFIG.task_id())
+        .find_or_create("build.windows_uwp_x64_dev." + CONFIG.tree_hash())
     )
 
 
@@ -339,7 +339,7 @@ def uwp_nightly():
         )
         .with_artifacts(appx_artifact(debug=False))
         .with_max_run_time_minutes(3 * 60)
-        .find_or_create("build.windows_uwp_nightlies." + CONFIG.task_id())
+        .find_or_create("build.windows_uwp_nightlies." + CONFIG.tree_hash())
     )
 
 
@@ -369,7 +369,7 @@ def windows_unit(cached=True):
                         "repo/target/debug/msi/Servo.zip")
     )
     if cached:
-        return task.find_or_create("build.windows_x64_dev." + CONFIG.task_id())
+        return task.find_or_create("build.windows_x64_dev." + CONFIG.tree_hash())
     else:
         return task.create()
 
@@ -386,7 +386,7 @@ def windows_nightly():
                      "mach upload-nightly windows-msvc --secret-from-taskcluster")
         .with_artifacts("repo/target/release/msi/Servo.exe",
                         "repo/target/release/msi/Servo.zip")
-        .find_or_create("build.windows_x64_nightly." + CONFIG.task_id())
+        .find_or_create("build.windows_x64_nightly." + CONFIG.tree_hash())
     )
 
 
@@ -403,7 +403,7 @@ def linux_nightly():
             "./mach upload-nightly linux --secret-from-taskcluster",
         )
         .with_artifacts("/repo/target/release/servo-tech-demo.tar.gz")
-        .find_or_create("build.linux_x64_nightly" + CONFIG.task_id())
+        .find_or_create("build.linux_x64_nightly" + CONFIG.tree_hash())
     )
 
 
@@ -415,7 +415,7 @@ def linux_release():
             "./mach build --release",
             "./mach package --release",
         )
-        .find_or_create("build.linux_x64_release" + CONFIG.task_id())
+        .find_or_create("build.linux_x64_release" + CONFIG.tree_hash())
     )
 
 
@@ -434,7 +434,7 @@ def macos_nightly():
             "./mach upload-nightly mac --secret-from-taskcluster",
         )
         .with_artifacts("repo/target/release/servo-tech-demo.dmg")
-        .find_or_create("build.mac_x64_nightly." + CONFIG.task_id())
+        .find_or_create("build.mac_x64_nightly." + CONFIG.tree_hash())
     )
 
 
@@ -477,7 +477,7 @@ def macos_release_build_with_debug_assertions(priority=None):
             " target/release/build/osmesa-src-*/out/src/mapi/shared-glapi/.libs",
         ]))
         .with_artifacts("repo/target.tar.gz")
-        .find_or_create("build.macos_x64_release_w_assertions." + CONFIG.task_id())
+        .find_or_create("build.macos_x64_release_w_assertions." + CONFIG.tree_hash())
     )
 
 
@@ -509,7 +509,7 @@ def linux_release_build_with_debug_assertions(layout_2020):
         .with_artifacts("/target.tar.gz")
         .find_or_create("build.linux_x64%s_release_w_assertions.%s" % (
             index_key_suffix,
-            CONFIG.task_id(),
+            CONFIG.tree_hash(),
         ))
     )
 
@@ -659,7 +659,7 @@ def wpt_chunks(platform, make_chunk_task, build_task, total_chunks, processes,
             platform.replace(" ", "_").lower(),
             job_id_prefix.replace("-", "_"),
             this_chunk,
-            CONFIG.task_id(),
+            CONFIG.tree_hash(),
         ))
 
 
diff --git a/etc/taskcluster/decisionlib.py b/etc/taskcluster/decisionlib.py
index 34cc634e5c2..cb899319ea5 100644
--- a/etc/taskcluster/decisionlib.py
+++ b/etc/taskcluster/decisionlib.py
@@ -64,14 +64,14 @@ class Config:
         self.default_provisioner_id = "proj-example"
 
 
-    def task_id(self):
-        if not hasattr(self, "_task_id"):
+    def tree_hash(self):
+        if not hasattr(self, "_tree_hash"):
             # Use the SHA-1 hash of the git "tree" object rather than the commit.
             # A `@bors-servo retry` command creates a new merge commit with a different commit hash
             # but with the same tree hash.
             output = subprocess.check_output(["git", "show", "-s", "--format=%T", "HEAD"])
-            self._task_id = output.decode("utf-8").strip()
-        return self._task_id
+            self._tree_hash = output.decode("utf-8").strip()
+        return self._tree_hash
 
     def git_sha_is_current_head(self):
         output = subprocess.check_output(["git", "rev-parse", "HEAD"])