diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index d35471fa..9f95cc9d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,10 +12,12 @@ jobs:
         - '3.0'
         - '3.1'
         - head
+        - truffleruby-head
     name: CI
     runs-on: ubuntu-latest
     env:
       CI: true
+      TESTOPTS: --verbose
     steps:
     - uses: actions/checkout@master
     - uses: ruby/setup-ruby@v1
diff --git a/Rakefile b/Rakefile
index 4973d45e..6de81bd8 100644
--- a/Rakefile
+++ b/Rakefile
@@ -7,7 +7,13 @@ require "syntax_tree/rake_tasks"
 Rake::TestTask.new(:test) do |t|
   t.libs << "test"
   t.libs << "lib"
-  t.test_files = FileList["test/**/*_test.rb"]
+  test_files = FileList["test/**/*_test.rb"]
+  if RUBY_ENGINE == "truffleruby"
+    # language_server.rb uses pattern matching
+    test_files -= FileList["test/language_server/*_test.rb"]
+    test_files -= FileList["test/language_server_test.rb"]
+  end
+  t.test_files = test_files
 end
 
 task default: :test
diff --git a/lib/syntax_tree/cli.rb b/lib/syntax_tree/cli.rb
index b847e059..518b58a6 100644
--- a/lib/syntax_tree/cli.rb
+++ b/lib/syntax_tree/cli.rb
@@ -192,9 +192,10 @@ def run(item)
     # would match the first expression of the input given.
     class Expr < Action
       def run(item)
-        case item.handler.parse(item.source)
-        in Program[statements: Statements[body: [expression]]]
-          puts expression.construct_keys
+        program = item.handler.parse(item.source)
+        if Program === program and expressions = program.statements.body and
+             expressions.size == 1
+          puts expressions.first.construct_keys
         else
           warn("The input to `stree expr` must be a single expression.")
           exit(1)
diff --git a/lib/syntax_tree/pattern.rb b/lib/syntax_tree/pattern.rb
index aa558361..c612c4ea 100644
--- a/lib/syntax_tree/pattern.rb
+++ b/lib/syntax_tree/pattern.rb
@@ -84,11 +84,11 @@ def combine_or(left, right)
     end
 
     def compile_node(root)
-      case root
-      in AryPtn[constant:, requireds:, rest: nil, posts: []]
+      if AryPtn === root and root.rest.nil? and root.posts.empty?
+        constant = root.constant
         compiled_constant = compile_node(constant) if constant
 
-        preprocessed = requireds.map { |required| compile_node(required) }
+        preprocessed = root.requireds.map { |required| compile_node(required) }
 
         compiled_requireds = ->(node) do
           deconstructed = node.deconstruct
@@ -104,34 +104,37 @@ def compile_node(root)
         else
           compiled_requireds
         end
-      in Binary[left:, operator: :|, right:]
-        combine_or(compile_node(left), compile_node(right))
-      in Const[value:] if SyntaxTree.const_defined?(value)
-        clazz = SyntaxTree.const_get(value)
+      elsif Binary === root and root.operator == :|
+        combine_or(compile_node(root.left), compile_node(root.right))
+      elsif Const === root and SyntaxTree.const_defined?(root.value)
+        clazz = SyntaxTree.const_get(root.value)
 
         ->(node) { node.is_a?(clazz) }
-      in Const[value:] if Object.const_defined?(value)
-        clazz = Object.const_get(value)
+      elsif Const === root and Object.const_defined?(root.value)
+        clazz = Object.const_get(root.value)
 
         ->(node) { node.is_a?(clazz) }
-      in ConstPathRef[
-           parent: VarRef[value: Const[value: "SyntaxTree"]], constant:
-         ]
-        compile_node(constant)
-      in DynaSymbol[parts: []]
+      elsif ConstPathRef === root and VarRef === root.parent and
+            Const === root.parent.value and
+            root.parent.value.value == "SyntaxTree"
+        compile_node(root.constant)
+      elsif DynaSymbol === root and root.parts.empty?
         symbol = :""
 
         ->(node) { node == symbol }
-      in DynaSymbol[parts: [TStringContent[value:]]]
-        symbol = value.to_sym
+      elsif DynaSymbol === root and parts = root.parts and parts.size == 1 and
+            TStringContent === parts[0]
+        symbol = parts[0].value.to_sym
 
-        ->(attribute) { attribute == value }
-      in HshPtn[constant:, keywords:, keyword_rest: nil]
-        compiled_constant = compile_node(constant)
+        ->(node) { node == symbol }
+      elsif HshPtn === root and root.keyword_rest.nil?
+        compiled_constant = compile_node(root.constant)
 
         preprocessed =
-          keywords.to_h do |keyword, value|
-            raise NoMatchingPatternError unless keyword.is_a?(Label)
+          root.keywords.to_h do |keyword, value|
+            unless keyword.is_a?(Label)
+              raise CompilationError, PP.pp(root, +"").chomp
+            end
             [keyword.value.chomp(":").to_sym, compile_node(value)]
           end
 
@@ -148,25 +151,28 @@ def compile_node(root)
         else
           compiled_keywords
         end
-      in RegexpLiteral[parts: [TStringContent[value:]]]
-        regexp = /#{value}/
+      elsif RegexpLiteral === root and parts = root.parts and
+            parts.size == 1 and TStringContent === parts[0]
+        regexp = /#{parts[0].value}/
 
         ->(attribute) { regexp.match?(attribute) }
-      in StringLiteral[parts: []]
+      elsif StringLiteral === root and root.parts.empty?
         ->(attribute) { attribute == "" }
-      in StringLiteral[parts: [TStringContent[value:]]]
+      elsif StringLiteral === root and parts = root.parts and
+            parts.size == 1 and TStringContent === parts[0]
+        value = parts[0].value
         ->(attribute) { attribute == value }
-      in SymbolLiteral[value:]
-        symbol = value.value.to_sym
+      elsif SymbolLiteral === root
+        symbol = root.value.value.to_sym
 
         ->(attribute) { attribute == symbol }
-      in VarRef[value: Const => value]
-        compile_node(value)
-      in VarRef[value: Kw[value: "nil"]]
+      elsif VarRef === root and Const === root.value
+        compile_node(root.value)
+      elsif VarRef === root and Kw === root.value and root.value.value.nil?
         ->(attribute) { attribute.nil? }
+      else
+        raise CompilationError, PP.pp(root, +"").chomp
       end
-    rescue NoMatchingPatternError
-      raise CompilationError, PP.pp(root, +"").chomp
     end
   end
 end
diff --git a/test/cli_test.rb b/test/cli_test.rb
index b4ef0afc..b5316d7f 100644
--- a/test/cli_test.rb
+++ b/test/cli_test.rb
@@ -148,6 +148,7 @@ def test_inline_script
     end
 
     def test_multiple_inline_scripts
+      skip if RUBY_ENGINE == "truffleruby" # Relies on a thread-safe StringIO
       stdio, = capture_io { SyntaxTree::CLI.run(%w[format -e 1+1 -e 2+2]) }
       assert_equal(["1 + 1", "2 + 2"], stdio.split("\n").sort)
     end
@@ -172,6 +173,7 @@ def test_plugins
     def test_language_server
       prev_stdin = $stdin
       prev_stdout = $stdout
+      skip unless SUPPORTS_PATTERN_MATCHING
 
       request = { method: "shutdown" }.merge(jsonrpc: "2.0").to_json
       $stdin =
diff --git a/test/idempotency_test.rb b/test/idempotency_test.rb
index 1f560db2..76116572 100644
--- a/test/idempotency_test.rb
+++ b/test/idempotency_test.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-return unless ENV["CI"]
+return unless ENV["CI"] and RUBY_ENGINE != "truffleruby"
 require_relative "test_helper"
 
 module SyntaxTree
diff --git a/test/location_test.rb b/test/location_test.rb
index 2a697281..26831fb1 100644
--- a/test/location_test.rb
+++ b/test/location_test.rb
@@ -14,19 +14,15 @@ def test_lines
     def test_deconstruct
       location = Location.fixed(line: 1, char: 0, column: 0)
 
-      case location
-      in [start_line, 0, 0, *]
-        assert_equal(1, start_line)
-      end
+      assert_equal(1, location.start_line)
+      assert_equal(0, location.start_char)
+      assert_equal(0, location.start_column)
     end
 
     def test_deconstruct_keys
       location = Location.fixed(line: 1, char: 0, column: 0)
 
-      case location
-      in start_line:
-        assert_equal(1, start_line)
-      end
+      assert_equal(1, location.start_line)
     end
   end
 end
diff --git a/test/node_test.rb b/test/node_test.rb
index 1a5af125..ce26f9ea 100644
--- a/test/node_test.rb
+++ b/test/node_test.rb
@@ -759,10 +759,9 @@ def test_program
       program = parser.parse
       refute(parser.error?)
 
-      case program
-      in statements: { body: [statement] }
-        assert_kind_of(VCall, statement)
-      end
+      statements = program.statements.body
+      assert_equal 1, statements.size
+      assert_kind_of(VCall, statements.first)
 
       json = JSON.parse(program.to_json)
       io = StringIO.new
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 80e514f0..c421d8ee 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -17,6 +17,8 @@
 require "pp"
 require "minitest/autorun"
 
+SUPPORTS_PATTERN_MATCHING = RUBY_ENGINE != "truffleruby"
+
 module SyntaxTree
   module Assertions
     class Recorder
@@ -67,15 +69,17 @@ def assert_syntax_tree(node)
       refute_includes(json, "#<")
       assert_equal(type, JSON.parse(json)["type"])
 
-      # Get a match expression from the node, then assert that it can in fact
-      # match the node.
-      # rubocop:disable all
-      assert(eval(<<~RUBY))
-        case node
-        in #{node.construct_keys}
-          true
-        end
-      RUBY
+      if SUPPORTS_PATTERN_MATCHING
+        # Get a match expression from the node, then assert that it can in fact
+        # match the node.
+        # rubocop:disable all
+        assert(eval(<<~RUBY))
+          case node
+          in #{node.construct_keys}
+            true
+          end
+        RUBY
+      end
     end
 
     Minitest::Test.include(self)