diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index a1ac9162b..73a9883b9 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -540,10 +540,12 @@
 #endif
 
 // Does the compiler support type_traits?
+// - full support of type traits was added only to GCC 5.1.0.
+// - 20150626 corresponds to the last release of 4.x libstdc++
 #ifndef EIGEN_HAS_TYPE_TRAITS
 #if EIGEN_MAX_CPP_VER>=11 && (EIGEN_HAS_CXX11 || EIGEN_COMP_MSVC >= 1700) \
-  && ((!EIGEN_COMP_GNUC_STRICT) || EIGEN_GNUC_AT_LEAST(5, 1)) \ // Full support of type traits was added only to GCC 5.1.0.
-  && ((!defined(__GLIBCXX__))   || __GLIBCXX__ > 20150626)      // The last release of 4.x libstdc++
+  && ((!EIGEN_COMP_GNUC_STRICT) || EIGEN_GNUC_AT_LEAST(5, 1)) \
+  && ((!defined(__GLIBCXX__))   || __GLIBCXX__ > 20150626)
 #define EIGEN_HAS_TYPE_TRAITS 1
 #define EIGEN_INCLUDE_TYPE_TRAITS
 #else