diff --git a/Eigen/Core b/Eigen/Core
index adab50b4a..2174c6bf8 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -180,7 +180,7 @@
     #undef bool
     #undef vector
     #undef pixel
-  #elif defined  __ARM_NEON__
+  #elif defined  __ARM_NEON
     #define EIGEN_VECTORIZE
     #define EIGEN_VECTORIZE_NEON
     #include <arm_neon.h>