diff --git a/Eigen/Core b/Eigen/Core
index 16007d0c9..8a261d167 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -178,7 +178,7 @@
     #undef bool
     #undef vector
     #undef pixel
-  #elif defined  __ARM_NEON
+  #elif (defined  __ARM_NEON) || (defined __ARM_NEON__)
     #define EIGEN_VECTORIZE
     #define EIGEN_VECTORIZE_NEON
     #include <arm_neon.h>