diff --git a/source/simulation2/components/CCmpTerritoryManager.cpp b/source/simulation2/components/CCmpTerritoryManager.cpp
index 577c4d5dfd..ca0ced11d7 100644
--- a/source/simulation2/components/CCmpTerritoryManager.cpp
+++ b/source/simulation2/components/CCmpTerritoryManager.cpp
@@ -451,9 +451,7 @@ void CCmpTerritoryManager::CalculateTerritories()
 			FloodFill(entityGrid, influenceGrid, openTiles, falloff);
 
 			// TODO: we should do a sparse grid and only add the non-zero regions, for performance
-			for (u16 j = 0; j < entityGrid.m_H; ++j)
-				for (u16 i = 0; i < entityGrid.m_W; ++i)
-					playerGrid.set(i, j, playerGrid.get(i, j) + entityGrid.get(i, j));
+			playerGrid.add(entityGrid);
 		}
 
 		playerGrids.push_back(std::make_pair(it->first, playerGrid));
diff --git a/source/simulation2/helpers/Grid.h b/source/simulation2/helpers/Grid.h
index 1a47b028f3..ba5bf77ec1 100644
--- a/source/simulation2/helpers/Grid.h
+++ b/source/simulation2/helpers/Grid.h
@@ -82,6 +82,17 @@ public:
 			memset(m_Data, 0, m_W*m_H*sizeof(T));
 	}
 
+	// Add two grids of the same size
+	void add(const Grid& g)
+	{
+#if GRID_BOUNDS_DEBUG
+		ENSURE(g.m_W == m_W && g.m_H == m_H);
+#endif
+		for (int j=0; j < m_H; ++j)
+			for (int i=0; i < m_W; ++i)
+				m_Data[j*m_W + i] += g.m_Data[j*m_W + i];
+	}
+
 	void set(int i, int j, const T& value)
 	{
 #if GRID_BOUNDS_DEBUG