diff --git a/include/boost/config/platform/qnxnto.hpp b/include/boost/config/platform/qnxnto.hpp
index 36eda4b2..b1377c8d 100644
--- a/include/boost/config/platform/qnxnto.hpp
+++ b/include/boost/config/platform/qnxnto.hpp
@@ -12,8 +12,11 @@
 #define BOOST_HAS_UNISTD_H
 #include <boost/config/posix_features.hpp>
 
-// QNX claims XOpen version 5 compatibility, but doesn't have an nl_types.h:
+// QNX claims XOpen version 5 compatibility, but doesn't have an nl_types.h
+// or log1p and expm1:
 #undef  BOOST_HAS_NL_TYPES_H
+#undef  BOOST_HAS_LOG1P
+#undef  BOOST_HAS_EXPM1
 
 #define BOOST_HAS_PTHREADS
 #define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE