diff --git a/gtk2_ardour/au_pluginui.mm b/gtk2_ardour/au_pluginui.mm
index 0434511f14..09f3eaf25b 100644
--- a/gtk2_ardour/au_pluginui.mm
+++ b/gtk2_ardour/au_pluginui.mm
@@ -867,6 +867,7 @@ AUPluginUI::cocoa_view_resized ()
 		for (unsigned long i = 0; i < [subviews count]; ++i) {
 			NSView* subview = [subviews objectAtIndex:i];
 			[subview setFrame:NSMakeRect (0, 0, new_frame.size.width, new_frame.size.height)];
+			break; /* only resize first subview */
 		}
 
 		/* also be sure to redraw the topbox because this can
@@ -1092,6 +1093,7 @@ AUPluginUI::parent_cocoa_window ()
 	for (unsigned long i = 0; i < [subviews count]; ++i) {
 		NSView* subview = [subviews objectAtIndex:i];
 		[subview setFrame:NSMakeRect (0, 0, req_width, req_height)];
+		break; /* only resize first subview */
 	}
 
 	last_au_frame = [au_view frame];
diff --git a/gtk2_ardour/mac_vst_plugin_ui.mm b/gtk2_ardour/mac_vst_plugin_ui.mm
index 082bfa99fc..4666264b97 100644
--- a/gtk2_ardour/mac_vst_plugin_ui.mm
+++ b/gtk2_ardour/mac_vst_plugin_ui.mm
@@ -222,6 +222,7 @@ MacVSTPluginUI::lower_box_size_allocate (Gtk::Allocation& allocation)
 	for (unsigned long i = 0; i < [subviews count]; ++i) {
 		NSView* subview = [subviews objectAtIndex:i];
 		[subview setFrame:NSMakeRect (0, 0, allocation.get_width (), allocation.get_height ())];
+		break; /* only resize first subview */
 	}
 }
 
diff --git a/gtk2_ardour/vst3_nsview_plugin_ui.mm b/gtk2_ardour/vst3_nsview_plugin_ui.mm
index b5b665ba09..50e32de071 100644
--- a/gtk2_ardour/vst3_nsview_plugin_ui.mm
+++ b/gtk2_ardour/vst3_nsview_plugin_ui.mm
@@ -153,6 +153,7 @@ VST3NSViewPluginUI::view_size_allocate (Gtk::Allocation& allocation)
 	for (unsigned long i = 0; i < [subviews count]; ++i) {
 		NSView* subview = [subviews objectAtIndex:i];
 		[subview setFrame:NSMakeRect (0, 0, allocation.get_width (), allocation.get_height ())];
+		break; /* only resize first subview */
 	}
 }