diff --git a/libs/ardour/ardour/luaproc.h b/libs/ardour/ardour/luaproc.h
index 314879a3d0..38d4961480 100644
--- a/libs/ardour/ardour/luaproc.h
+++ b/libs/ardour/ardour/luaproc.h
@@ -87,6 +87,7 @@ public:
 	void cleanup () { }
 
 	int set_block_size (pframes_t /*nframes*/) { return 0; }
+	bool requires_fixed_sized_buffers () const { return _requires_fixed_sized_buffers; }
 	bool connect_all_audio_outputs () const { return _connect_all_audio_outputs; }
 
 	int connect_and_run (BufferSet& bufs,
@@ -163,6 +164,7 @@ private:
 	std::string _docs;
 	bool _lua_does_channelmapping;
 	bool _lua_has_inline_display;
+	bool _requires_fixed_sized_buffers;
 	bool _connect_all_audio_outputs;
 	bool _set_time_info;
 
diff --git a/libs/ardour/luaproc.cc b/libs/ardour/luaproc.cc
index 4c5cdda35f..bef72ee0d2 100644
--- a/libs/ardour/luaproc.cc
+++ b/libs/ardour/luaproc.cc
@@ -60,6 +60,7 @@ LuaProc::LuaProc (AudioEngine& engine,
 	, _script (script)
 	, _lua_does_channelmapping (false)
 	, _lua_has_inline_display (false)
+	, _requires_fixed_sized_buffers (false)
 	, _connect_all_audio_outputs (false)
 	, _set_time_info (false)
 	, _designated_bypass_port (UINT32_MAX)
@@ -300,6 +301,9 @@ LuaProc::load_script ()
 					if (i.key().cast<std::string> () == "time_info" && i.value().isBoolean ()) {
 						_set_time_info = i.value().cast<bool> ();
 					}
+					if (i.key().cast<std::string> () == "regular_block_length" && i.value().isBoolean ()) {
+						_requires_fixed_sized_buffers = i.value().cast<bool> ();
+					}
 				}
 			}
 		} catch (...) {