diff --git a/Eigen/src/Core/products/SelfadjointMatrixMatrix.h b/Eigen/src/Core/products/SelfadjointMatrixMatrix.h
index cc9333384..563feb094 100644
--- a/Eigen/src/Core/products/SelfadjointMatrixMatrix.h
+++ b/Eigen/src/Core/products/SelfadjointMatrixMatrix.h
@@ -262,6 +262,8 @@ struct ei_product_selfadjoint_matrix<Scalar,Index,LhsStorageOrder,true,Conjugate
     Index mc = rows;  // cache block size along the M direction
     Index nc = cols;  // cache block size along the N direction
     computeProductBlockingSizes<Scalar,Scalar>(kc, mc, nc);
+    // kc must smaller than mc
+    kc = std::min(kc,mc);
 
     Scalar* blockA = ei_aligned_stack_new(Scalar, kc*mc);
     std::size_t sizeB = kc*Blocking::PacketSize*Blocking::nr + kc*cols;