diff --git a/Cache/ConcreteBlockCache.cpp b/Cache/ConcreteBlockCache.cpp
index d18ccb3..5bf7ede 100644
--- a/Cache/ConcreteBlockCache.cpp
+++ b/Cache/ConcreteBlockCache.cpp
@@ -58,6 +58,10 @@ using ProFUSE::POSIXException;
 //typedef std::vector<ConcreteBlockCache::Entry *>::iterator EntryIter;
 
 
+BlockCachePointer ConcreteBlockCache::Create(BlockDevicePointer device, unsigned size)
+{
+    return BlockCachePointer(new ConcreteBlockCache(device, size));
+}
 
 ConcreteBlockCache::ConcreteBlockCache(BlockDevicePointer device, unsigned size) :
     BlockCache(device)
diff --git a/Cache/ConcreteBlockCache.h b/Cache/ConcreteBlockCache.h
index 8191be0..aead0e6 100644
--- a/Cache/ConcreteBlockCache.h
+++ b/Cache/ConcreteBlockCache.h
@@ -9,7 +9,9 @@ namespace Device {
 
 class ConcreteBlockCache : public BlockCache {
 public:
-    ConcreteBlockCache(BlockDevicePointer device, unsigned size = 16);
+
+    static BlockCachePointer Create(BlockDevicePointer device, unsigned size = 16);
+
     virtual ~ConcreteBlockCache();
 
     virtual void sync();
@@ -21,8 +23,11 @@ public:
     virtual void markDirty(unsigned block);
 
     
-
 private:
+    
+    
+    ConcreteBlockCache(BlockDevicePointer device, unsigned size);
+    
     struct Entry {
         unsigned block;
         unsigned count;
diff --git a/Cache/MappedBlockCache.cpp b/Cache/MappedBlockCache.cpp
index 46fb1b2..4a65fb1 100644
--- a/Cache/MappedBlockCache.cpp
+++ b/Cache/MappedBlockCache.cpp
@@ -19,6 +19,11 @@ using namespace Device;
 using ProFUSE::Exception;
 using ProFUSE::POSIXException;
 
+BlockCachePointer MappedBlockCache::Create(BlockDevicePointer device, void *data)
+{
+    return BlockCachePointer(new MappedBlockCache(device, data));
+}
+
 
 MappedBlockCache::MappedBlockCache(BlockDevicePointer device, void *data) :
     BlockCache(device)
diff --git a/Cache/MappedBlockCache.h b/Cache/MappedBlockCache.h
index c36ab3c..e02a854 100644
--- a/Cache/MappedBlockCache.h
+++ b/Cache/MappedBlockCache.h
@@ -8,7 +8,8 @@ namespace Device {
 class MappedBlockCache : public BlockCache {
     public:
 
-    MappedBlockCache(BlockDevicePointer device, void *data);
+    static BlockCachePointer Create(BlockDevicePointer device, void *data);
+
     virtual ~MappedBlockCache();
 
     virtual void sync();
@@ -22,7 +23,9 @@ class MappedBlockCache : public BlockCache {
     virtual void markDirty(unsigned block);
 
     private:
-    
+
+    MappedBlockCache(BlockDevicePointer device, void *data);
+
     void sync(unsigned block);
         
     uint8_t *_data;
diff --git a/Device/BlockDevice.cpp b/Device/BlockDevice.cpp
index de126c7..d421746 100644
--- a/Device/BlockDevice.cpp
+++ b/Device/BlockDevice.cpp
@@ -237,5 +237,5 @@ BlockCachePointer BlockDevice::createBlockCache()
 {
     unsigned b = blocks();
     unsigned size = std::max(16u, b / 16);
-    return BlockCachePointer(new ConcreteBlockCache(shared_from_this(), size));
+    return ConcreteBlockCache::Create(shared_from_this(), size);
 }
diff --git a/Device/DavexDiskImage.cpp b/Device/DavexDiskImage.cpp
index c4392fb..7600d5b 100644
--- a/Device/DavexDiskImage.cpp
+++ b/Device/DavexDiskImage.cpp
@@ -161,6 +161,6 @@ DavexDiskImage *DavexDiskImage::Create(const char *name, size_t blocks, const ch
 BlockCachePointer DavexDiskImage::createBlockCache()
 {
     // need a smart pointer, but only have this....
-    return BlockCachePointer(new MappedBlockCache(shared_from_this(), 512 + (uint8_t *)address()));
+    return MappedBlockCache::Create(shared_from_this(), 512 + (uint8_t *)address());
     
 }
diff --git a/Device/DiskCopy42Image.cpp b/Device/DiskCopy42Image.cpp
index 122017f..3d121f3 100644
--- a/Device/DiskCopy42Image.cpp
+++ b/Device/DiskCopy42Image.cpp
@@ -224,5 +224,5 @@ BlockCachePointer DiskCopy42Image::createBlockCache()
     
     if (!readOnly()) _changed = true;
     
-    return BlockCachePointer(new MappedBlockCache(shared_from_this(), address()));
+    return MappedBlockCache::Create(shared_from_this(), address());
 }
\ No newline at end of file
diff --git a/Device/DiskImage.cpp b/Device/DiskImage.cpp
index fe1761a..091d789 100644
--- a/Device/DiskImage.cpp
+++ b/Device/DiskImage.cpp
@@ -140,7 +140,7 @@ void ProDOSOrderDiskImage::Validate(MappedFile *f)
 
 BlockCachePointer ProDOSOrderDiskImage::createBlockCache()
 {
-    return BlockCachePointer(new MappedBlockCache(shared_from_this(), address()));
+    return MappedBlockCache::Create(shared_from_this(), address());
 }
 
 #pragma mark -
diff --git a/Device/UniversalDiskImage.cpp b/Device/UniversalDiskImage.cpp
index 4464e88..1d7014e 100644
--- a/Device/UniversalDiskImage.cpp
+++ b/Device/UniversalDiskImage.cpp
@@ -145,7 +145,7 @@ BlockCachePointer UniversalDiskImage::createBlockCache()
 {
     if (_format == 1)
     {
-        return BlockCachePointer(new MappedBlockCache(shared_from_this(), _dataOffset + (uint8_t *)address()));
+        return MappedBlockCache::Create(shared_from_this(), _dataOffset + (uint8_t *)address());
     }
     
     return DiskImage::createBlockCache();