diff --git a/Cache/MappedBlockCache.cpp b/Cache/MappedBlockCache.cpp
index ba17efe..1d1be58 100644
--- a/Cache/MappedBlockCache.cpp
+++ b/Cache/MappedBlockCache.cpp
@@ -64,6 +64,12 @@ void MappedBlockCache::release(unsigned block, int flags)
 
 void MappedBlockCache::write(unsigned block, const void *vp)
 {
+#undef __METHOD__
+#define __METHOD__ "MappedBlockCache::write"
+    
+    if (block >= blocks())
+        throw Exception(__METHOD__ ": Invalid block.");
+    
     _dirty = true;
     std::memcpy(_data + block * 512, vp, 512);
 }
@@ -71,6 +77,13 @@ void MappedBlockCache::write(unsigned block, const void *vp)
 
 void MappedBlockCache::zeroBlock(unsigned block)
 {
+#undef __METHOD__
+#define __METHOD__ "MappedBlockCache::zeroBlock"
+    
+    if (block >= blocks())
+        throw Exception(__METHOD__ ": Invalid block.");
+    
+    
     _dirty = true;
     std::memset(_data + block * 512, 0, 512);
 }
diff --git a/Cache/MappedBlockCache.h b/Cache/MappedBlockCache.h
index 951a974..a3402ff 100644
--- a/Cache/MappedBlockCache.h
+++ b/Cache/MappedBlockCache.h
@@ -22,11 +22,11 @@ class MappedBlockCache : public BlockCache {
     virtual void markDirty(unsigned block);
 
     private:
-        void sync(unsigned block);
+    
+    void sync(unsigned block);
         
-        uint8_t *_data;
-        bool _dirty;
-
+    uint8_t *_data;
+    bool _dirty;
 };
 
 } // namespace