diff --git a/.github/workflows/formatters.yml b/.github/workflows/formatters.yml
index b114eea2..4df38b69 100644
--- a/.github/workflows/formatters.yml
+++ b/.github/workflows/formatters.yml
@@ -5,9 +5,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout pull request
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0 # compare against main
       - name: Fetch master
         run: |
           git fetch
diff --git a/test/formatters/apheleia-ft.el b/test/formatters/apheleia-ft.el
index b560441b..77f8115e 100755
--- a/test/formatters/apheleia-ft.el
+++ b/test/formatters/apheleia-ft.el
@@ -56,6 +56,39 @@ already in memory on the current branch."
       (goto-char (point-min))
       (read (current-buffer)))))
 
+(defun apheleia-ft--get-changed-files-for-pull-request ()
+  "Return list of files (relative to repo root) changed in this PR.
+This means added, removed, or changed compared to main."
+  (let ((stderr-file (make-temp-file "apheleia-ft-stderr-")))
+    (with-temp-buffer
+      (let ((exit-status
+             (call-process
+              "git" nil (list (current-buffer) stderr-file) nil
+              "diff" "--name-only" "origin/main...HEAD")))
+        (unless (zerop exit-status)
+          (with-temp-buffer
+            (insert-file-contents stderr-file)
+            (princ (buffer-string)))
+          (error
+           (concat
+            "Failed to 'git diff --name-only "
+            "origin/main...HEAD', got exit status %S")
+           exit-status)))
+      (split-string (buffer-string)))))
+
+(defun apheleia-ft--get-formatters-with-changed-scripts ()
+  "Return list of formatter symbols whose scripts were touched in this PR.
+This means their install scripts are different from how they
+appear on main. This may include formatters that were removed
+relative to main."
+  (save-match-data
+    (let ((formatters nil))
+      (dolist (file (apheleia-ft--get-changed-files-for-pull-request))
+        (when (string-match
+               "\\`test/formatters/installers/\\([^./]+\\)\\.bash\\'" file)
+          (push (intern (match-string 1 file)) formatters)))
+      formatters)))
+
 (defun apheleia-ft--get-formatters-for-pull-request ()
   "Return list of formatter string names that were touched in this PR.
 This means their commands in `apheleia-formatters' are different
@@ -63,10 +96,13 @@ from how they appear on main, or they were added relative to
 main."
   (let ((old-formatters (apheleia-ft--get-formatters-from-ref "origin/main"))
         (new-formatters apheleia-formatters)
+        (formatters-with-changed-scripts
+         (apheleia-ft--get-formatters-with-changed-scripts))
         (touched-formatters nil))
     (map-do
      (lambda (formatter command)
-       (unless (equal command (alist-get formatter old-formatters))
+       (unless (and (equal command (alist-get formatter old-formatters))
+                    (not (memq formatter formatters-with-changed-scripts)))
          (push (symbol-name formatter) touched-formatters)))
      new-formatters)
     touched-formatters))
@@ -273,6 +309,7 @@ environment variable, defaulting to all formatters."
                         out-temp-file)
                        ((guard (stringp arg))
                         arg)
+                       (`npx arg)
                        (_ (eval arg))))
                    command))
             (setq command (delq 'npx command))
diff --git a/test/formatters/build-image.bash b/test/formatters/build-image.bash
index a118d12b..3c3d4612 100755
--- a/test/formatters/build-image.bash
+++ b/test/formatters/build-image.bash
@@ -17,6 +17,11 @@ if [[ "$OSTYPE" != darwin* ]] && [[ "$EUID" != 0 ]]; then
     docker=(sudo -E "${docker[@]}")
 fi
 
-exec "${docker[@]}" build .                    \
-     -t "apheleia-formatters:${TAG:-latest}"   \
-     --build-arg "FORMATTERS=${FORMATTERS:-}"
+no_cache=()
+if [[ -n "${NO_CACHE:-}" ]]; then
+    no_cache=("--no-cache")
+fi
+
+exec "${docker[@]}" build . \
+    -t "apheleia-formatters:${TAG:-latest}" \
+    --build-arg "FORMATTERS=${FORMATTERS:-}" "${no_cache[@]}"
diff --git a/test/formatters/installers/prettier-ruby.bash b/test/formatters/installers/prettier-ruby.bash
index 611f5c63..0be3df07 100644
--- a/test/formatters/installers/prettier-ruby.bash
+++ b/test/formatters/installers/prettier-ruby.bash
@@ -4,12 +4,6 @@ apt-get install -y ruby ruby-dev gcc
 # Install the plugin
 npm install -g prettier @prettier/plugin-ruby
 
-# Have to install from source because release not tagged yet
-# https://github.com/ruby-syntax-tree/syntax_tree-rbs/pull/34
-# https://stackoverflow.com/a/11767563
-gem install specific_install
-gem specific_install -l https://github.com/ruby-syntax-tree/syntax_tree-rbs.git
-
 # These are required dependencies documented at
 # https://www.npmjs.com/package/@prettier/plugin-ruby
 gem install prettier_print syntax_tree syntax_tree-haml syntax_tree-rbs