diff --git a/Eigen/Core b/Eigen/Core
index 07d82d155..0b2608036 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -125,7 +125,7 @@
   #endif
 #endif
 
-#ifdef _OPENMP
+#if (defined _OPENMP) && (!defined EIGEN_DONT_PARALLELIZE)
   #define EIGEN_HAS_OPENMP
 #endif