diff --git a/Eigen/src/Core/IO.h b/Eigen/src/Core/IO.h
index dfd9097cc..2198f5668 100644
--- a/Eigen/src/Core/IO.h
+++ b/Eigen/src/Core/IO.h
@@ -131,9 +131,7 @@ struct significant_decimals_default_impl
   typedef typename NumTraits<Scalar>::Real RealScalar;
   static inline int run()
   {
-    using std::ceil;
-    using std::log;
-    return cast<RealScalar,int>(ceil(-log(NumTraits<RealScalar>::epsilon())/log(RealScalar(10))));
+    return cast<RealScalar,int>(numext::ceil(-numext::log(NumTraits<RealScalar>::epsilon())/numext::log(RealScalar(10))));
   }
 };