diff --git a/src/tools/imgtool/imgtool.cpp b/src/tools/imgtool/imgtool.cpp
index 57a702dd17b..12adfe533d3 100644
--- a/src/tools/imgtool/imgtool.cpp
+++ b/src/tools/imgtool/imgtool.cpp
@@ -518,7 +518,7 @@ imgtoolerr_t imgtool::image::list_partitions(std::vector<imgtool::partition_info
 	else
 	{
 		// default implementation
-		partitions.emplace_back(unknown_partition_get_info, 0, ~0);
+		partitions.emplace_back(module().imgclass, 0, ~0);
 	}
 	return IMGTOOLERR_SUCCESS;	
 }
@@ -560,9 +560,8 @@ uint64_t imgtool::image::rand()
 //  imgtool::partition ctor
 //-------------------------------------------------
 
-imgtool::partition::partition(imgtool::image &image, imgtool_class &imgclass, int partition_index, uint64_t base_block, uint64_t block_count)
+imgtool::partition::partition(imgtool::image &image, const imgtool_class &imgclass, int partition_index, uint64_t base_block, uint64_t block_count)
 	: m_image(image)
-	//, m_partition_index(partition_index)
 	, m_base_block(base_block)
 	, m_block_count(block_count)
 	, m_imgclass(imgclass)
@@ -635,9 +634,7 @@ imgtoolerr_t imgtool::partition::open(imgtool::image &image, int partition_index
 {
 	imgtoolerr_t err = (imgtoolerr_t)IMGTOOLERR_SUCCESS;
 	imgtool::partition::ptr p;
-	imgtool_class imgclass;
 	std::vector<imgtool::partition_info> partitions;
-	uint64_t base_block, block_count;
 	imgtoolerr_t (*open_partition)(imgtool::partition &partition, uint64_t first_block, uint64_t block_count);
 
 	// list the partitions
@@ -646,14 +643,13 @@ imgtoolerr_t imgtool::partition::open(imgtool::image &image, int partition_index
 		return err;
 
 	// is this an invalid index?
-	if ((partition_index < 0) || (partition_index >= partitions.size()) || !partitions[partition_index].get_info())
+	if ((partition_index < 0) || (partition_index >= partitions.size()) || (!partitions[partition_index].imgclass().get_info && !partitions[partition_index].imgclass().derived_get_info))
 		return IMGTOOLERR_INVALIDPARTITION;
 
 	// use this partition 
-	memset(&imgclass, 0, sizeof(imgclass));
-	imgclass.get_info = partitions[partition_index].get_info();
-	base_block = partitions[partition_index].base_block();
-	block_count = partitions[partition_index].block_count();
+	const imgtool_class &imgclass(partitions[partition_index].imgclass());
+	uint64_t base_block = partitions[partition_index].base_block();
+	uint64_t block_count = partitions[partition_index].block_count();
 
 	// allocate the new partition object
 	try { p = std::make_unique<imgtool::partition>(image, imgclass, partition_index, base_block, block_count); }
diff --git a/src/tools/imgtool/imgtool.h b/src/tools/imgtool/imgtool.h
index b1b09462c42..8d40e109fb8 100644
--- a/src/tools/imgtool/imgtool.h
+++ b/src/tools/imgtool/imgtool.h
@@ -144,7 +144,7 @@ namespace imgtool
 		typedef std::unique_ptr<partition> ptr;
 
 		// ctor/dtor
-		partition(imgtool::image &image, imgtool_class &imgclass, int partition_index, uint64_t base_block, uint64_t block_count);
+		partition(imgtool::image &image, const imgtool_class &imgclass, int partition_index, uint64_t base_block, uint64_t block_count);
 		~partition();
 
 		static imgtoolerr_t open(imgtool::image &image, int partition_index, ptr &partition);
diff --git a/src/tools/imgtool/library.h b/src/tools/imgtool/library.h
index e7ddf46ade0..59b75be447d 100644
--- a/src/tools/imgtool/library.h
+++ b/src/tools/imgtool/library.h
@@ -244,18 +244,26 @@ namespace imgtool
 	{
 	public:
 		partition_info(imgtool_get_info get_info, uint64_t base_block, uint64_t block_count)
-			: m_get_info(get_info)
+			: m_base_block(base_block)
+			, m_block_count(block_count)
+		{
+			memset(&m_imgclass, 0, sizeof(m_imgclass));
+			m_imgclass.get_info = get_info;
+		}
+
+		partition_info(imgtool_class imgclass, uint64_t base_block, uint64_t block_count)
+			: m_imgclass(imgclass)
 			, m_base_block(base_block)
 			, m_block_count(block_count)
 		{
 		}
 
-		imgtool_get_info get_info() const { return m_get_info; }
+		const imgtool_class &imgclass() const { return m_imgclass; }
 		uint64_t base_block() const { return m_base_block; }
 		uint64_t block_count() const { return m_block_count; }
 
 	private:
-		imgtool_get_info    m_get_info;
+		imgtool_class			m_imgclass;
 		uint64_t                m_base_block;
 		uint64_t                m_block_count;
 	};