diff --git a/include/qpdf/QPDFExc.hh b/include/qpdf/QPDFExc.hh
index 7d6d896..884ad03 100644
--- a/include/qpdf/QPDFExc.hh
+++ b/include/qpdf/QPDFExc.hh
@@ -12,6 +12,7 @@
 #include <qpdf/Constants.h>
 #include <stdexcept>
 #include <fcntl.h>
+#include <stdlib.h>
 
 class DLL_EXPORT QPDFExc: public std::runtime_error
 {