--- qpdf-2.3.1/include/qpdf/QPDFExc.hh
+++ qpdf-2.3.1/include/qpdf/QPDFExc.hh
@@ -11,6 +11,7 @@
 #include <qpdf/DLL.h>
 #include <qpdf/Constants.h>
 #include <stdexcept>
+#include <unistd.h>
 
 class QPDFExc: public std::runtime_error
 {
--- qpdf-2.3.1/include/qpdf/QPDFObjectHandle.hh
+++ qpdf-2.3.1/include/qpdf/QPDFObjectHandle.hh
@@ -8,6 +8,7 @@
 #ifndef __QPDFOBJECTHANDLE_HH__
 #define __QPDFOBJECTHANDLE_HH__
 
+#include <unistd.h>
 #include <string>
 #include <vector>
 #include <set>