diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index 2de1d76..3911885 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -354,7 +354,7 @@ void
 QUtil::setLineBuf(FILE* f)
 {
 #ifndef _WIN32
-    setvbuf(f, reinterpret_cast<char *>(NULL), _IOLBF, 0);
+    setvbuf(f, reinterpret_cast<char *>(0), _IOLBF, 0);
 #endif
 }