diff --git a/libqpdf/Pl_Buffer.cc b/libqpdf/Pl_Buffer.cc
index 1ca9292d..d11959f4 100644
--- a/libqpdf/Pl_Buffer.cc
+++ b/libqpdf/Pl_Buffer.cc
@@ -1,5 +1,6 @@
 #include <qpdf/Pl_Buffer.hh>
 #include <stdexcept>
+#include <algorithm>
 #include <assert.h>
 #include <string.h>