diff --git a/common/gal/opengl/cached_container.cpp b/common/gal/opengl/cached_container.cpp
index cadeed9f91..d9e966164e 100644
--- a/common/gal/opengl/cached_container.cpp
+++ b/common/gal/opengl/cached_container.cpp
@@ -45,7 +45,7 @@
 using namespace KIGFX;
 
 CACHED_CONTAINER::CACHED_CONTAINER( unsigned int aSize ) :
-    VERTEX_CONTAINER( aSize ), m_item( NULL ), m_chunkSize( 0 ), m_chunkOffset( 0 )
+    VERTEX_CONTAINER( aSize ), m_item( NULL ), m_chunkSize( 0 ), m_chunkOffset( 0 ), m_maxIndex( 0 )
 {
     // In the beginning there is only free space
     m_freeChunks.insert( std::make_pair( aSize, 0 ) );
@@ -84,6 +84,8 @@ void CACHED_CONTAINER::FinishItem()
         // Add the not used memory back to the pool
         addFreeChunk( itemOffset + itemSize, m_chunkSize - itemSize );
         // mergeFreeChunks();   // veery slow and buggy
+
+        m_maxIndex = std::max( itemOffset + itemSize, m_maxIndex );
     }
 
     if( itemSize > 0 )
@@ -189,6 +191,7 @@ void CACHED_CONTAINER::Delete( VERTEX_ITEM* aItem )
 void CACHED_CONTAINER::Clear()
 {
     m_freeSpace = m_currentSize;
+    m_maxIndex = 0;
     m_failed = false;
 
     // Set the size of all the stored VERTEX_ITEMs to 0, so it is clear that they are not held
@@ -305,6 +308,8 @@ void CACHED_CONTAINER::defragment( VERTEX* aTarget )
         m_item->setOffset( newOffset );
         m_chunkOffset = newOffset;
     }
+
+    m_maxIndex = usedSpace();
 }
 
 
diff --git a/common/gal/opengl/cached_container_ram.cpp b/common/gal/opengl/cached_container_ram.cpp
index b6eff40b2a..a306373dfa 100644
--- a/common/gal/opengl/cached_container_ram.cpp
+++ b/common/gal/opengl/cached_container_ram.cpp
@@ -64,7 +64,7 @@ void CACHED_CONTAINER_RAM::Unmap()
     // Upload vertices coordinates and shader types to GPU memory
     glBindBuffer( GL_ARRAY_BUFFER, m_verticesBuffer );
     checkGlError( "binding vertices buffer" );
-    glBufferData( GL_ARRAY_BUFFER, usedSpace() * VERTEX_SIZE, m_vertices, GL_STREAM_DRAW );
+    glBufferData( GL_ARRAY_BUFFER, m_maxIndex * VERTEX_SIZE, m_vertices, GL_STREAM_DRAW );
     checkGlError( "transferring vertices" );
     glBindBuffer( GL_ARRAY_BUFFER, 0 );
     checkGlError( "unbinding vertices buffer" );
@@ -110,6 +110,7 @@ bool CACHED_CONTAINER_RAM::defragmentResize( unsigned int aNewSize )
     // Now there is only one big chunk of free memory
     m_freeChunks.clear();
     m_freeChunks.insert( std::make_pair( m_freeSpace, m_currentSize - m_freeSpace ) );
+    m_dirty = true;
 
     return true;
 }
diff --git a/include/gal/opengl/cached_container.h b/include/gal/opengl/cached_container.h
index 299c997262..70cd32e28a 100644
--- a/include/gal/opengl/cached_container.h
+++ b/include/gal/opengl/cached_container.h
@@ -103,6 +103,9 @@ protected:
     unsigned int m_chunkSize;
     unsigned int m_chunkOffset;
 
+    ///> Maximal vertex index number stored in the container
+    unsigned int m_maxIndex;
+
     /**
      * Resizes the chunk that stores the current item to the given size. The current item has
      * its offset adjusted after the call, and the new chunk parameters are stored