diff --git a/include/boost/iostreams/detail/system_failure.hpp b/include/boost/iostreams/detail/system_failure.hpp
index c90c288..ea59f10 100755
--- a/include/boost/iostreams/detail/system_failure.hpp
+++ b/include/boost/iostreams/detail/system_failure.hpp
@@ -20,7 +20,7 @@
 #include <boost/iostreams/detail/config/windows_posix.hpp>
 #include <boost/iostreams/detail/ios.hpp>  // failure.
 
-#ifdef BOOST_NO_STDC_NAMESPACE
+#ifdef BOOST_NO_STDC_NAMESPACE && !defined(__LIBCOMO__)
 namespace std { using ::strlen; }
 #endif
 
diff --git a/include/boost/iostreams/filter/test.hpp b/include/boost/iostreams/filter/test.hpp
index f0a1a97..1e08123 100755
--- a/include/boost/iostreams/filter/test.hpp
+++ b/include/boost/iostreams/filter/test.hpp
@@ -48,7 +48,7 @@
 #undef rand
 #undef strlen
 
-#if defined(BOOST_NO_STDC_NAMESPACE) || defined(__LIBCOMO__)
+#if defined(BOOST_NO_STDC_NAMESPACE) && !defined(__LIBCOMO__)
 namespace std { 
     using ::memcpy; 
     using ::strlen;