diff --git a/Eigen/src/Core/util/Memory.h b/Eigen/src/Core/util/Memory.h
index a8583c812..cc14f098a 100644
--- a/Eigen/src/Core/util/Memory.h
+++ b/Eigen/src/Core/util/Memory.h
@@ -43,7 +43,7 @@
   #define EIGEN_MALLOC_ALREADY_ALIGNED 0
 #endif
 
-#if ((defined _GNU_SOURCE) || ((defined _XOPEN_SOURCE) && (_XOPEN_SOURCE >= 600))) && (defined _POSIX_ADVISORY_INFO) && (_POSIX_ADVISORY_INFO > 0)
+#if (defined __QNXNTO__) || (((defined _GNU_SOURCE) || ((defined _XOPEN_SOURCE) && (_XOPEN_SOURCE >= 600))) && (defined _POSIX_ADVISORY_INFO) && (_POSIX_ADVISORY_INFO > 0))
   #define EIGEN_HAS_POSIX_MEMALIGN 1
 #else
   #define EIGEN_HAS_POSIX_MEMALIGN 0