diff --git a/Eigen/src/SparseCore/SparseCompressedBase.h b/Eigen/src/SparseCore/SparseCompressedBase.h
index fb795a0ed..c223e4f42 100644
--- a/Eigen/src/SparseCore/SparseCompressedBase.h
+++ b/Eigen/src/SparseCore/SparseCompressedBase.h
@@ -95,7 +95,12 @@ class SparseCompressedBase
     
     /** \returns whether \c *this is in compressed form. */
     inline bool isCompressed() const { return innerNonZeroPtr()==0; }
-  
+
+  protected:
+    /** Default constructor. Do nothing. */
+    SparseCompressedBase() {}
+  private:
+    template<typename OtherDerived> explicit SparseCompressedBase(const SparseCompressedBase<OtherDerived>&);
 };
 
 template<typename Derived>