diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.mods/refresh.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.mods/refresh.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.mods/refresh.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.mods/refresh.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // bool copy_file(const path& from, const path& to);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.file_size/file_size.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.file_size/file_size.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.file_size/file_size.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.file_size/file_size.pass.cpp
@@ -8,6 +8,10 @@
 
 // UNSUPPORTED: c++03
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // uintmax_t file_size(const path& p);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
@@ -10,6 +10,10 @@
 
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
+// The string reported on errors changed, which makes those tests fail when run
+// against already-released libc++'s.
+// XFAIL: with_system_cxx_lib=macosx10.15
+
 // <filesystem>
 
 // file_time_type last_write_time(const path& p);
diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -317,31 +317,28 @@
         - exit_status: -1  # Agent was lost
           limit: 2
 
-  # TODO: Re-enable those as soon as Green Dragon is back online. Currently,
-  #       all the jobs are failing when they try to pull the older dylibs from
-  #       Green Dragon, which is down.
-  # # Test back-deployment to older Apple platforms
-  # - label: "Apple back-deployment macosx10.9"
-  #   command: "libcxx/utils/ci/run-buildbot x86_64-apple-system-backdeployment-10.9"
-  #   artifact_paths:
-  #     - "**/test-results.xml"
-  #   agents:
-  #     queue: "libcxx-builders-macos10.15" # TODO: For now, we're running the back-deployment tests for 10.9 on 10.15, because we don't have proper 10.9 machines
-  #   retry:
-  #     automatic:
-  #       - exit_status: -1  # Agent was lost
-  #         limit: 2
-
-  # - label: "Apple back-deployment macosx10.15"
-  #   command: "libcxx/utils/ci/run-buildbot x86_64-apple-system-backdeployment-10.15"
-  #   artifact_paths:
-  #     - "**/test-results.xml"
-  #   agents:
-  #     queue: "libcxx-builders-macos10.15"
-  #   retry:
-  #     automatic:
-  #       - exit_status: -1  # Agent was lost
-  #         limit: 2
+  # Test back-deployment to older Apple platforms
+  - label: "Apple back-deployment macosx10.9"
+    command: "libcxx/utils/ci/run-buildbot x86_64-apple-system-backdeployment-10.9"
+    artifact_paths:
+      - "**/test-results.xml"
+    agents:
+      queue: "libcxx-builders-macos10.15" # TODO: For now, we're running the back-deployment tests for 10.9 on 10.15, because we don't have proper 10.9 machines
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
+
+  - label: "Apple back-deployment macosx10.15"
+    command: "libcxx/utils/ci/run-buildbot x86_64-apple-system-backdeployment-10.15"
+    artifact_paths:
+      - "**/test-results.xml"
+    agents:
+      queue: "libcxx-builders-macos10.15"
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
 
   - label: "AArch64"
     command: "libcxx/utils/ci/run-buildbot aarch64"
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -295,7 +295,7 @@
 
     if [[ "${OSX_ROOTS}" == "" ]]; then
         echo "--- Downloading previous macOS dylibs"
-        PREVIOUS_DYLIBS_URL="http://lab.llvm.org:8080/roots/libcxx-roots.tar.gz"
+        PREVIOUS_DYLIBS_URL="https://dl.dropboxusercontent.com/s/liu4fmc53qzlfly/libcxx-roots.tar.gz"
         OSX_ROOTS="${BUILD_DIR}/macos-roots"
         mkdir -p "${OSX_ROOTS}"
         curl "${PREVIOUS_DYLIBS_URL}" | tar -xz --strip-components=1 -C "${OSX_ROOTS}"