diff --git a/src/mapblock.cpp b/src/mapblock.cpp
index e0e4c5c64..d88395762 100644
--- a/src/mapblock.cpp
+++ b/src/mapblock.cpp
@@ -101,11 +101,12 @@ static const char *modified_reason_strings[] = {
 */
 
 MapBlock::MapBlock(v3s16 pos, IGameDef *gamedef):
+		m_is_mono_block(true),
 		m_pos(pos),
 		m_pos_relative(pos * MAP_BLOCKSIZE),
 		m_gamedef(gamedef)
 {
-	reallocate(nodecount, MapNode(CONTENT_IGNORE));
+	reallocate(1, MapNode(CONTENT_IGNORE));
 }
 
 MapBlock::~MapBlock()
@@ -222,25 +223,27 @@ void MapBlock::copyFrom(const VoxelManipulator &src)
 	v3s16 data_size(MAP_BLOCKSIZE, MAP_BLOCKSIZE, MAP_BLOCKSIZE);
 	VoxelArea data_area(v3s16(0,0,0), data_size - v3s16(1,1,1));
 
-	deconvertMonoblock();
+	expandNodesIfNeeded();
 	// Copy from VoxelManipulator to data
 	src.copyTo(data, data_area, v3s16(0,0,0),
 			getPosRelative(), data_size);
-	tryConvertToMonoblock();
+	tryShrinkNodes();
 }
 
 void MapBlock::reallocate(u32 c, MapNode n)
 {
 	delete[] data;
-	if (c == 1)
+	if (!m_is_mono_block && c == 1)
 		porting::TrackFreedMemory(sizeof(MapNode) * nodecount);
 
 	data = new MapNode[c];
 	for (u32 i = 0; i < c; i++)
 		data[i] = n;
+
+	m_is_mono_block = (c == 1);
 }
 
-void MapBlock::tryConvertToMonoblock()
+void MapBlock::tryShrinkNodes()
 {
 	if (m_is_mono_block)
 		return;
@@ -255,7 +258,6 @@ void MapBlock::tryConvertToMonoblock()
 	}
 
 	if (is_mono_block) {
-		m_is_mono_block = true;
 		reallocate(1, n);
 		if (n.getContent() == CONTENT_AIR) {
 			m_is_air = true;
@@ -264,11 +266,10 @@ void MapBlock::tryConvertToMonoblock()
 	}
 }
 
-void MapBlock::deconvertMonoblock()
+void MapBlock::expandNodesIfNeeded()
 {
 	if (m_is_mono_block) {
 		reallocate(nodecount, data[0]);
-		m_is_mono_block = false;
 	}
 }
 
@@ -513,6 +514,7 @@ void MapBlock::deSerialize(std::istream &in_compressed, u8 version, bool disk)
 	TRACESTREAM(<<"MapBlock::deSerialize "<<getPos()<<std::endl);
 
 	m_is_air_expired = true;
+	expandNodesIfNeeded();
 
 	if(version <= 21)
 	{
@@ -642,7 +644,7 @@ void MapBlock::deSerialize(std::istream &in_compressed, u8 version, bool disk)
 		}
 
 		if (nimap.size() == 1) {
-			tryConvertToMonoblock();
+			tryShrinkNodes();
 			u16 dummy;
 			if (nimap.getId("air", dummy)) {
 				m_is_air = true;
diff --git a/src/mapblock.h b/src/mapblock.h
index 8effc6ce9..483964db5 100644
--- a/src/mapblock.h
+++ b/src/mapblock.h
@@ -76,7 +76,7 @@ public:
 
 	MapNode* getData()
 	{
-		deconvertMonoblock();
+		expandNodesIfNeeded();
 		return data;
 	}
 
@@ -250,7 +250,7 @@ public:
 		if (!isValidPosition(x, y, z))
 			throw InvalidPositionException();
 
-		deconvertMonoblock();
+		expandNodesIfNeeded();
 		data[z * zstride + y * ystride + x] = n;
 		raiseModified(MOD_STATE_WRITE_NEEDED, MOD_REASON_SET_NODE);
 	}
@@ -276,7 +276,7 @@ public:
 
 	inline void setNodeNoCheck(s16 x, s16 y, s16 z, MapNode n)
 	{
-		deconvertMonoblock();
+		expandNodesIfNeeded();
 		data[z * zstride + y * ystride + x] = n;
 		raiseModified(MOD_STATE_WRITE_NEEDED, MOD_REASON_SET_NODE);
 	}
@@ -441,9 +441,9 @@ private:
 
 	void deSerialize_pre22(std::istream &is, u8 version, bool disk);
 	// check if all nodes are identical, if so store them as a single node
-	void tryConvertToMonoblock();
+	void tryShrinkNodes();
 	// if only a single node is stored, expand storage back to the full array
-	void deconvertMonoblock();
+	void expandNodesIfNeeded();
 	void reallocate(u32 c, MapNode n);
 
 	/*
@@ -464,7 +464,7 @@ public:
 private:
 	// see isOrphan()
 	bool m_orphan = false;
-	bool m_is_mono_block = false;
+	bool m_is_mono_block;
 
 	// Position in blocks on parent
 	v3s16 m_pos;
diff --git a/src/unittest/test_mapblock.cpp b/src/unittest/test_mapblock.cpp
index 4ca66c19c..3a89f2f3e 100644
--- a/src/unittest/test_mapblock.cpp
+++ b/src/unittest/test_mapblock.cpp
@@ -63,7 +63,7 @@ void TestMapBlock::testMonoblock(IGameDef *gamedef)
 		block.data[i] = MapNode(CONTENT_AIR);
 	}
 	// covert to monoblock
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(block.m_is_mono_block);
 	UASSERT(block.data[0].param0 == CONTENT_AIR);
 	UASSERT(block.data != t);
@@ -76,17 +76,17 @@ void TestMapBlock::testMonoblock(IGameDef *gamedef)
 	UASSERT(block.data == d1);
 
 	// covert back to mono block
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(block.m_is_mono_block);
 	t = block.data;
 
 	// deconvert explicitly
-	block.deconvertMonoblock();
+	block.expandNodesIfNeeded();
 	UASSERT(!block.m_is_mono_block);
 	UASSERT(block.data != t);
 
 	// covert back to mono block
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(block.m_is_mono_block);
 	t = block.data;
 
@@ -97,7 +97,7 @@ void TestMapBlock::testMonoblock(IGameDef *gamedef)
 	t = block.data;
 
 	// cannot covert to mono block
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(!block.m_is_mono_block);
 	UASSERT(block.data == t);
 
@@ -107,7 +107,7 @@ void TestMapBlock::testMonoblock(IGameDef *gamedef)
 	}
 
 	// can covert to mono block
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(block.m_is_mono_block);
 	UASSERT(block.data[0].param0 == 42);
 	UASSERT(block.data != t);
@@ -143,19 +143,19 @@ void TestMapBlock::testMonoblock(IGameDef *gamedef)
 	UASSERT(block.m_is_mono_block);
 
 	block.setNode(5,5,5,MapNode(23));
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(!block.m_is_mono_block);
 
 	block.setNode(5,5,5,MapNode(42, 1, 0));
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(!block.m_is_mono_block);
 
 	block.setNode(5,5,5,MapNode(42, 0, 1));
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(!block.m_is_mono_block);
 
 	block.setNode(5,5,5,MapNode(42));
-	block.tryConvertToMonoblock();
+	block.tryShrinkNodes();
 	UASSERT(block.m_is_mono_block);
 }