diff --git a/libs/ardour/ardour/lv2_plugin.h b/libs/ardour/ardour/lv2_plugin.h
index e5a8138a7f..6495db9430 100644
--- a/libs/ardour/ardour/lv2_plugin.h
+++ b/libs/ardour/ardour/lv2_plugin.h
@@ -188,10 +188,10 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 		_ui_scale_factor = s;
 	}
 	static void set_global_ui_style_boxy (bool yn) {
-		_ui_style_boxy = yn;
+		_ui_style_boxy = yn ? 1 : 0;
 	}
 	static void set_global_ui_style_flat (bool yn) {
-		_ui_style_flat = yn;
+		_ui_style_flat = yn ? 1 : 0;
 	}
 	static void set_main_window_id (unsigned long id) {
 		_ui_transient_win_id = id;
@@ -343,8 +343,8 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 
 	// Options passed to plugin
 	int32_t              _seq_size;
-	static bool          _ui_style_flat;
-	static bool          _ui_style_boxy;
+	static int32_t       _ui_style_flat;
+	static int32_t       _ui_style_boxy;
 	static uint32_t      _ui_background_color;
 	static uint32_t      _ui_foreground_color;
 	static uint32_t      _ui_contrasting_color;
diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index b562e23afb..43826c8f3f 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -129,8 +129,8 @@ using namespace ARDOUR;
 using namespace PBD;
 
 bool          LV2Plugin::force_state_save      = false;
-bool          LV2Plugin::_ui_style_flat        = false;
-bool          LV2Plugin::_ui_style_boxy        = false;
+int32_t       LV2Plugin::_ui_style_flat        = 0;
+int32_t       LV2Plugin::_ui_style_boxy        = 0;
 uint32_t      LV2Plugin::_ui_background_color  = 0x000000ff; // RGBA
 uint32_t      LV2Plugin::_ui_foreground_color  = 0xffffffff; // RGBA
 uint32_t      LV2Plugin::_ui_contrasting_color = 0x33ff33ff; // RGBA
@@ -577,9 +577,9 @@ LV2Plugin::init(const void* c_plugin, samplecnt_t rate)
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://lv2plug.in/ns/extensions/ui#scaleFactor"),
 		  sizeof(float), atom_Float, &_ui_scale_factor },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://ardour.org/lv2/theme/#styleBoxy"),
-		  sizeof(bool), atom_Bool, &_ui_style_boxy },
+		  sizeof(int32_t), atom_Bool, &_ui_style_boxy },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://ardour.org/lv2/theme/#styleFlat"),
-		  sizeof(bool), atom_Bool, &_ui_style_flat },
+		  sizeof(int32_t), atom_Bool, &_ui_style_flat },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://kxstudio.sf.net/ns/lv2ext/props#TransientWindowId"),
 		  sizeof(int32_t), atom_Long, &_ui_transient_win_id },
 		{ LV2_OPTIONS_INSTANCE, 0, 0, 0, 0, NULL }