2 files changed, 13 insertions, 0 deletions
diff --git a/lib/prism/polyfill/string.rb b/lib/prism/polyfill/string.rb
new file mode 100644
index 0000000000..582266d956
--- /dev/null
+++ b/lib/prism/polyfill/string.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+# Polyfill for String#unpack1 with the offset parameter.
+if String.instance_method(:unpack1).parameters.none? { |_, name| name == :offset }
+  String.prepend(
+    Module.new {
+      def unpack1(format, offset: 0) # :nodoc:
+        offset == 0 ? super(format) : self[offset..].unpack1(format) # steep:ignore
+      end
+    }
+  )
+end
diff --git a/lib/prism/prism.gemspec b/lib/prism/prism.gemspec
index 1ad2da35c4..d43fcfd36b 100644
--- a/lib/prism/prism.gemspec
+++ b/lib/prism/prism.gemspec
@@ -87,6 +87,7 @@ Gem::Specification.new do |spec|
     "lib/prism/parse_result/comments.rb",
     "lib/prism/parse_result/newlines.rb",
     "lib/prism/pattern.rb",
+    "lib/prism/polyfill/string.rb",
     "lib/prism/serialize.rb",
     "lib/prism/translation.rb",
     "lib/prism/translation/parser.rb",