diff --git a/include/ceres/internal/port.h b/include/ceres/internal/port.h
index 1193fcf..f4dcaee 100644
--- a/include/ceres/internal/port.h
+++ b/include/ceres/internal/port.h
@@ -33,9 +33,8 @@
 
 // This file needs to compile as c code.
 #ifdef __cplusplus
-
+#include <cstddef>
 #include "ceres/internal/config.h"
-#include "Eigen/Core"
 #if defined(CERES_TR1_MEMORY_HEADER)
 #include <tr1/memory>
 #else
@@ -57,7 +56,6 @@
 // what case we're in and write macros that do the right thing.
 #ifdef CERES_USE_CXX11
 namespace port_constants {
-
 static constexpr size_t kMaxAlignBytes =
     // Work around a GCC 4.8 bug
     // (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019) where
@@ -67,22 +65,7 @@
 #else
     alignof(std::max_align_t);
 #endif
-
-static constexpr bool kShouldAlignMatrix = 16 <= kMaxAlignBytes;
-static constexpr size_t kAlignment = kShouldAlignMatrix ? 16 : 1;
-
-static constexpr int kEigenAlignmentHint =
-    kShouldAlignMatrix ? Eigen::AutoAlign : Eigen::DontAlign;
 }  // namespace port_constants
-
-#define CERES_ALIGNMENT_SPECIFIER alignas(::ceres::port_constants::kAlignment)
-#define CERES_MATRIX_ALIGN_HINT ::ceres::port_constants::kEigenAlignmentHint
-
-#else // !CXX_11
-
-#define CERES_ALIGNMENT_SPECIFIER
-#define CERES_MATRIX_ALIGN_HINT Eigen::DontAlign
-
 #endif
 
 }  // namespace ceres
diff --git a/include/ceres/jet.h b/include/ceres/jet.h
index 8515be8..1e95eaa 100644
--- a/include/ceres/jet.h
+++ b/include/ceres/jet.h
@@ -228,8 +228,23 @@
   T a;
 
   // The infinitesimal part.
-  // See ceres/include/internal/port.h for meaning of the #defines here.
-  CERES_ALIGNMENT_SPECIFIER Eigen::Matrix<T, N, 1, CERES_MATRIX_ALIGN_HINT> v;
+
+  // We allocate Jets on the stack and other places they
+  // might not be aligned to 16-byte boundaries.  If we have C++11, we
+  // can specify their alignment anyway, and thus can safely enable
+  // vectorization on those matrices; in C++99, we are out of luck.  Figure out
+  // what case we're in and do the right thing.
+#ifndef CERES_USE_CXX11
+  // fall back to safe version:
+  Eigen::Matrix<T, N, 1, Eigen::DontAlign> v;
+#else
+  static constexpr bool kShouldAlignMatrix =
+      16 <= ::ceres::port_constants::kMaxAlignBytes;
+  static constexpr int kAlignHint = kShouldAlignMatrix ?
+      Eigen::AutoAlign : Eigen::DontAlign;
+  static constexpr size_t kAlignment = kShouldAlignMatrix ? 16 : 1;
+  alignas(kAlignment) Eigen::Matrix<T, N, 1, kAlignHint> v;
+#endif
 };
 
 // Unary +