diff --git a/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp b/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp
index 3a1e6f4a2..95631c301 100644
--- a/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp
+++ b/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp
@@ -21,7 +21,7 @@ subject to the following restrictions:
 
 btHeightfieldTerrainShape::btHeightfieldTerrainShape
 (
-int heightStickWidth, int heightStickLength, void* heightfieldData,
+int heightStickWidth, int heightStickLength, const void* heightfieldData,
 btScalar heightScale, btScalar minHeight, btScalar maxHeight,int upAxis,
 PHY_ScalarType hdt, bool flipQuadEdges
 )
@@ -33,7 +33,7 @@ PHY_ScalarType hdt, bool flipQuadEdges
 
 
 
-btHeightfieldTerrainShape::btHeightfieldTerrainShape(int heightStickWidth, int heightStickLength,void* heightfieldData,btScalar maxHeight,int upAxis,bool useFloatData,bool flipQuadEdges)
+btHeightfieldTerrainShape::btHeightfieldTerrainShape(int heightStickWidth, int heightStickLength,const void* heightfieldData,btScalar maxHeight,int upAxis,bool useFloatData,bool flipQuadEdges)
 {
 	// legacy constructor: support only float or unsigned char,
 	// 	and min height is zero
@@ -53,7 +53,7 @@ btHeightfieldTerrainShape::btHeightfieldTerrainShape(int heightStickWidth, int h
 
 void btHeightfieldTerrainShape::initialize
 (
-int heightStickWidth, int heightStickLength, void* heightfieldData,
+int heightStickWidth, int heightStickLength, const void* heightfieldData,
 btScalar heightScale, btScalar minHeight, btScalar maxHeight, int upAxis,
 PHY_ScalarType hdt, bool flipQuadEdges
 )
diff --git a/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h b/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h
index 710c29e08..78e231e08 100644
--- a/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h
+++ b/src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h
@@ -85,10 +85,10 @@ protected:
 	btScalar m_heightScale;
 	union
 	{
-		unsigned char*	m_heightfieldDataUnsignedChar;
-		short*		m_heightfieldDataShort;
-		btScalar*			m_heightfieldDataFloat;
-		void*			m_heightfieldDataUnknown;
+		const unsigned char*	m_heightfieldDataUnsignedChar;
+		const short*		m_heightfieldDataShort;
+		const btScalar*			m_heightfieldDataFloat;
+		const void*	m_heightfieldDataUnknown;
 	};
 
 	PHY_ScalarType	m_heightDataType;	
@@ -111,7 +111,7 @@ protected:
 	  backwards-compatible without a lot of copy/paste.
 	 */
 	void initialize(int heightStickWidth, int heightStickLength,
-	                void* heightfieldData, btScalar heightScale,
+	                const void* heightfieldData, btScalar heightScale,
 	                btScalar minHeight, btScalar maxHeight, int upAxis,
 	                PHY_ScalarType heightDataType, bool flipQuadEdges);
 
@@ -123,7 +123,7 @@ public:
 	  heightScale is needed for any integer-based heightfield data types.
 	 */
 	btHeightfieldTerrainShape(int heightStickWidth,int heightStickLength,
-	                          void* heightfieldData, btScalar heightScale,
+	                          const void* heightfieldData, btScalar heightScale,
 	                          btScalar minHeight, btScalar maxHeight,
 	                          int upAxis, PHY_ScalarType heightDataType,
 	                          bool flipQuadEdges);
@@ -135,7 +135,7 @@ public:
 	  compatibility reasons, heightScale is calculated as maxHeight / 65535 
 	  (and is only used when useFloatData = false).
  	 */
-	btHeightfieldTerrainShape(int heightStickWidth,int heightStickLength,void* heightfieldData, btScalar maxHeight,int upAxis,bool useFloatData,bool flipQuadEdges);
+	btHeightfieldTerrainShape(int heightStickWidth,int heightStickLength,const void* heightfieldData, btScalar maxHeight,int upAxis,bool useFloatData,bool flipQuadEdges);
 
 	virtual ~btHeightfieldTerrainShape();