diff --git a/libs/ardour/ardour/chan_mapping.h b/libs/ardour/ardour/chan_mapping.h
index 07b623f8e1..cc42ed01bc 100644
--- a/libs/ardour/ardour/chan_mapping.h
+++ b/libs/ardour/ardour/chan_mapping.h
@@ -25,13 +25,14 @@
 #include <ostream>
 #include <utility>
 
+#include "pbd/stack_allocator.h"
 #include "pbd/xml++.h"
+
 #include "ardour/data_type.h"
 #include "ardour/chan_count.h"
 
 namespace ARDOUR {
 
-
 /** A mapping from one set of channels to another.
  * The general form is  1 source (from), many sinks (to).
  * numeric IDs are used to identify sources and sinks.
@@ -103,8 +104,8 @@ public:
 	 */
 	bool     is_subset (const ChanMapping& superset) const;
 
-	typedef std::map<uint32_t, uint32_t>    TypeMapping;
-	typedef std::map<DataType, TypeMapping> Mappings;
+	typedef std::map<uint32_t, uint32_t, std::less<uint32_t>, PBD::StackAllocator<std::pair<const uint32_t, uint32_t>, 16> > TypeMapping;
+	typedef std::map<DataType, TypeMapping, std::less<DataType>, PBD::StackAllocator<std::pair<const DataType, TypeMapping>, 2> > Mappings;
 
 	Mappings        mappings()       { return _mappings; }
 	const Mappings& mappings() const { return _mappings; }
diff --git a/libs/ardour/ardour/plugin_insert.h b/libs/ardour/ardour/plugin_insert.h
index 68c1aaa604..003df28a38 100644
--- a/libs/ardour/ardour/plugin_insert.h
+++ b/libs/ardour/ardour/plugin_insert.h
@@ -29,6 +29,7 @@
 
 #include <boost/weak_ptr.hpp>
 
+#include "pbd/stack_allocator.h"
 #include "pbd/timing.h"
 
 #include "ardour/ardour.h"
@@ -370,7 +371,8 @@ private:
 	/* ordered map [plugin instance ID] => ARDOUR::ChanMapping
 	 * TODO: consider replacing with boost::flat_map<> or std::vector<>.
 	 */
-	class PinMappings : public std::map <uint32_t, ARDOUR::ChanMapping> {
+	class PinMappings : public std::map <uint32_t, ARDOUR::ChanMapping, std::less<uint32_t>, PBD::StackAllocator<std::pair<const uint32_t, ARDOUR::ChanMapping>, 4> > 
+	{
 		public:
 			/* this emulates C++11's  std::map::at()
 			 * return mapping for given plugin instance */