diff --git a/Eigen/src/SparseCore/CompressedStorage.h b/Eigen/src/SparseCore/CompressedStorage.h
index 4f36957..f408dd3 100644
--- a/Eigen/src/SparseCore/CompressedStorage.h
+++ b/Eigen/src/SparseCore/CompressedStorage.h
@@ -172,12 +172,31 @@
       size_t id = searchLowerIndex(0,m_size,key);
       if (id>=m_size || m_indices[id]!=key)
       {
-        resize(m_size+1,1);
-        for (size_t j=m_size-1; j>id; --j)
+        if (m_allocatedSize<m_size+1)
         {
-          m_indices[j] = m_indices[j-1];
-          m_values[j] = m_values[j-1];
+          m_allocatedSize = 2*(m_size+1);
+          internal::scoped_array<Scalar> newValues(m_allocatedSize);
+          internal::scoped_array<Index> newIndices(m_allocatedSize);
+
+          // copy first chunk
+          internal::smart_copy(m_values,  m_values +id, newValues.ptr());
+          internal::smart_copy(m_indices, m_indices+id, newIndices.ptr());
+
+          // copy the rest
+          if(m_size>id)
+          {
+            internal::smart_copy(m_values +id,  m_values +m_size, newValues.ptr() +id+1);
+            internal::smart_copy(m_indices+id,  m_indices+m_size, newIndices.ptr()+id+1);
+          }
+          std::swap(m_values,newValues.ptr());
+          std::swap(m_indices,newIndices.ptr());
         }
+        else if(m_size>id)
+        {
+          internal::smart_memmove(m_values +id, m_values +m_size, m_values +id+1);
+          internal::smart_memmove(m_indices+id, m_indices+m_size, m_indices+id+1);
+        }
+        m_size++;
         m_indices[id] = key;
         m_values[id] = defaultValue;
       }
diff --git a/test/sparse_vector.cpp b/test/sparse_vector.cpp
index 5eea9ed..5dc4219 100644
--- a/test/sparse_vector.cpp
+++ b/test/sparse_vector.cpp
@@ -23,8 +23,8 @@
   SparseVectorType v1(rows), v2(rows), v3(rows);
   DenseMatrix refM1 = DenseMatrix::Zero(rows, rows);
   DenseVector refV1 = DenseVector::Random(rows),
-    refV2 = DenseVector::Random(rows),
-    refV3 = DenseVector::Random(rows);
+              refV2 = DenseVector::Random(rows),
+              refV3 = DenseVector::Random(rows);
 
   std::vector<int> zerocoords, nonzerocoords;
   initSparse<Scalar>(densityVec, refV1, v1, &zerocoords, &nonzerocoords);
@@ -52,6 +52,20 @@
     }
   }
   VERIFY_IS_APPROX(v1, refV1);
+  
+  // test coeffRef with reallocation
+  {
+    SparseVectorType v1(rows);
+    DenseVector v2 = DenseVector::Zero(rows);
+    for(int k=0; k<rows; ++k)
+    {
+      int i = internal::random<int>(0,rows-1);
+      Scalar v = internal::random<Scalar>();
+      v1.coeffRef(i) += v;
+      v2.coeffRef(i) += v;
+    }
+    VERIFY_IS_APPROX(v1,v2);
+  }
 
   v1.coeffRef(nonzerocoords[0]) = Scalar(5);
   refV1.coeffRef(nonzerocoords[0]) = Scalar(5);