diff --git a/lib/rbs.rb b/lib/rbs.rb
index b4a8b6aa5..ac5ec76cb 100644
--- a/lib/rbs.rb
+++ b/lib/rbs.rb
@@ -69,7 +69,12 @@
 require "rbs/type_alias_regularity"
 require "rbs/collection"
 
-require "rbs_extension"
+begin
+  require "rbs_extension"
+rescue LoadError
+  require "rbs/ffi/parser"
+  require "rbs/ffi/location"
+end
 require "rbs/parser_aux"
 require "rbs/location_aux"
 
diff --git a/lib/rbs/ffi/location.rb b/lib/rbs/ffi/location.rb
new file mode 100644
index 000000000..ca4686553
--- /dev/null
+++ b/lib/rbs/ffi/location.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module RBS
+  class Location
+    def initialize(buffer, start_pos, end_pos)
+
+    end
+
+    def initialize_copy(other)
+
+    end
+
+    def buffer
+
+    end
+
+    def _start_pos
+
+    end
+
+    def _end_pos
+
+    end
+
+    def _add_required_child(name, start, end_pos)
+
+    end
+
+    def _add_optional_child(name, start, end_pos)
+
+    end
+
+    def _add_optional_no_child(name)
+
+    end
+
+    def _optional_keys
+
+    end
+
+    def _required_keys
+
+    end
+
+    def [](name)
+
+    end
+  end
+end
\ No newline at end of file
diff --git a/lib/rbs/ffi/parser.rb b/lib/rbs/ffi/parser.rb
new file mode 100644
index 000000000..c143ba855
--- /dev/null
+++ b/lib/rbs/ffi/parser.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module RBS
+  class Parser
+    def _parse_type(buffer, start_pos, end_pos, variables, require_eof)
+
+    end
+
+    def _parse_method_type(buffer, start_pos, end_pos, variables, require_eof)
+
+    end
+
+    def _parse_signature(buffer, start_pos, end_pos)
+
+    end
+
+    def _parse_type_params(buffer, start_pos, end_pos, module_type_params)
+
+    end
+
+    def _parse_inline_leading_annotation(buffer, start_pos, end_pos, variables)
+
+    end
+
+    def _parse_inline_trailing_annotation(buffer, start_pos, end_pos, variables)
+
+    end
+  end
+end