diff --git a/include/boost/math/special_functions/expm1.hpp b/include/boost/math/special_functions/expm1.hpp
index feba014e9..a73a99389 100644
--- a/include/boost/math/special_functions/expm1.hpp
+++ b/include/boost/math/special_functions/expm1.hpp
@@ -7,6 +7,7 @@
 #define BOOST_MATH_EXPM1_INCLUDED
 
 #include <cmath>
+#include <math.h> // platform's ::expm1
 #include <boost/limits.hpp>
 #include <boost/math/special_functions/detail/series.hpp>