diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index 1b3517123e..5ad4192080 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -333,10 +333,24 @@ private:
 	 * which is known to be troublesome with Visual C++ :-
 	 * https://www.boost.org/doc/libs/1_65_0/libs/type_traits/doc/html/boost_typetraits/reference/aligned_storage.html
 	 */
-	typedef std::map <uint32_t, ARDOUR::ChanMapping> PinMappings;
+	class PinMappings : public std::map <uint32_t, ARDOUR::ChanMapping>
 #else
-	typedef std::map <uint32_t, ARDOUR::ChanMapping, std::less<uint32_t>, PBD::StackAllocator<std::pair<const uint32_t, ARDOUR::ChanMapping>, 4> > PinMappings;
+	class PinMappings : public std::map <uint32_t, ARDOUR::ChanMapping, std::less<uint32_t>, PBD::StackAllocator<std::pair<const uint32_t, ARDOUR::ChanMapping>, 4> >
 #endif
+	{
+		public:
+			/* this emulates C++11's  std::map::at()
+			 * return mapping for given plugin instance */
+			inline ARDOUR::ChanMapping const& p (const uint32_t i) const {
+#ifndef NDEBUG
+				const_iterator x = find (i);
+				assert (x != end ());
+				return x->second;
+#else
+				return find(i)->second;
+#endif
+			}
+	};
 
 	PinMappings _in_map;
 	PinMappings _out_map;
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index fa51bf1bf8..e69f67ea06 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -916,11 +916,11 @@ PluginInsert::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t e
 				continue;
 			}
 			bool valid;
-			uint32_t first_idx = in_map.at(0).get (*t, 0, &valid);
+			uint32_t first_idx = in_map.p(0).get (*t, 0, &valid);
 			assert (valid && first_idx == 0); // check_inplace ensures this
 			/* copy the first stream's buffer contents to the others */
 			for (uint32_t i = 1; i < natural_input_streams ().get (*t); ++i) {
-				uint32_t idx = in_map.at(0).get (*t, i, &valid);
+				uint32_t idx = in_map.p(0).get (*t, i, &valid);
 				if (valid) {
 					x_assert (idx, idx == 0);
 					bufs.get_available (*t, i).read_from (bufs.get_available (*t, first_idx), nframes, offset, offset);
@@ -1034,7 +1034,7 @@ PluginInsert::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t e
 			for (DataType::iterator t = DataType::begin(); t != DataType::end(); ++t) {
 				for (uint32_t out = 0; out < natural_output_streams().get (*t); ++out) {
 					bool valid;
-					uint32_t out_idx = out_map.at(pc).get (*t, out, &valid);
+					uint32_t out_idx = out_map.p(pc).get (*t, out, &valid);
 					if (valid) {
 						used_outputs.set (*t, out_idx, 1); // mark as used
 					}
@@ -1066,14 +1066,14 @@ PluginInsert::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t e
 		for (Plugins::iterator i = _plugins.begin(); i != _plugins.end(); ++i, ++pc) {
 
 			ARDOUR::ChanMapping i_in_map (natural_input_streams());
-			ARDOUR::ChanMapping i_out_map (out_map.at(pc));
+			ARDOUR::ChanMapping i_out_map (out_map.p(pc));
 			ARDOUR::ChanCount mapped;
 
 			/* map inputs sequentially */
 			for (DataType::iterator t = DataType::begin(); t != DataType::end(); ++t) {
 				for (uint32_t in = 0; in < natural_input_streams().get (*t); ++in) {
 					bool valid;
-					uint32_t in_idx = in_map.at(pc).get (*t, in, &valid);
+					uint32_t in_idx = in_map.p(pc).get (*t, in, &valid);
 					uint32_t m = mapped.get (*t);
 					if (valid) {
 						inplace_bufs.get_available (*t, m).read_from (bufs.get_available (*t, in_idx), nframes, offset, offset);
@@ -1120,7 +1120,7 @@ PluginInsert::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t e
 		/* in-place processing */
 		uint32_t pc = 0;
 		for (Plugins::iterator i = _plugins.begin(); i != _plugins.end(); ++i, ++pc) {
-			if ((*i)->connect_and_run(bufs, start, end, speed, in_map.at(pc), out_map.at(pc), nframes, offset)) {
+			if ((*i)->connect_and_run(bufs, start, end, speed, in_map.p(pc), out_map.p(pc), nframes, offset)) {
 				deactivate ();
 			}
 		}
@@ -2608,9 +2608,9 @@ PluginInsert::state () const
 	for (uint32_t pc = 0; pc < get_count(); ++pc) {
 		char tmp[128];
 		snprintf (tmp, sizeof(tmp), "InputMap-%d", pc);
-		node.add_child_nocopy (* _in_map.at (pc).state (tmp));
+		node.add_child_nocopy (* _in_map.p (pc).state (tmp));
 		snprintf (tmp, sizeof(tmp), "OutputMap-%d", pc);
-		node.add_child_nocopy (* _out_map.at (pc).state (tmp));
+		node.add_child_nocopy (* _out_map.p (pc).state (tmp));
 	}
 	node.add_child_nocopy (* _thru_map.state ("ThruMap"));