diff --git a/include/PolyVox/AmbientOcclusionCalculator.h b/include/PolyVox/AmbientOcclusionCalculator.h
index bdd10de7..72f80bf1 100644
--- a/include/PolyVox/AmbientOcclusionCalculator.h
+++ b/include/PolyVox/AmbientOcclusionCalculator.h
@@ -74,7 +74,7 @@ namespace PolyVox
 	
 	/// Calculate the ambient occlusion for the volume
 	template<typename VolumeType, typename IsVoxelTransparentCallback>
-	void calculateAmbientOcclusion(VolumeType* volInput, Array<3, uint8_t>* arrayResult, Region region, float fRayLength, uint8_t uNoOfSamplesPerOutputElement, IsVoxelTransparentCallback isVoxelTransparentCallback);
+	void calculateAmbientOcclusion(VolumeType* volInput, Array<3, uint8_t>* arrayResult, const Region& region, float fRayLength, uint8_t uNoOfSamplesPerOutputElement, IsVoxelTransparentCallback isVoxelTransparentCallback);
 }
 
 #include "PolyVox/AmbientOcclusionCalculator.inl"
diff --git a/include/PolyVox/AmbientOcclusionCalculator.inl b/include/PolyVox/AmbientOcclusionCalculator.inl
index be9db40e..cea5897a 100644
--- a/include/PolyVox/AmbientOcclusionCalculator.inl
+++ b/include/PolyVox/AmbientOcclusionCalculator.inl
@@ -32,7 +32,7 @@ namespace PolyVox
 	 * \param isVoxelTransparentCallback A callback which takes a \a VoxelType and returns a \a bool whether the voxel is transparent
 	 */
 	template<typename VolumeType, typename IsVoxelTransparentCallback>
-	void calculateAmbientOcclusion(VolumeType* volInput, Array<3, uint8_t>* arrayResult, Region region, float fRayLength, uint8_t uNoOfSamplesPerOutputElement, IsVoxelTransparentCallback isVoxelTransparentCallback)
+	void calculateAmbientOcclusion(VolumeType* volInput, Array<3, uint8_t>* arrayResult, const Region& region, float fRayLength, uint8_t uNoOfSamplesPerOutputElement, IsVoxelTransparentCallback isVoxelTransparentCallback)
 	{
 		//Make sure that the size of the volume is an exact multiple of the size of the array.
 		if(volInput->getWidth() % arrayResult->getDimension(0) != 0)