diff --git a/src/vanillapdf/utils/buffer.h b/src/vanillapdf/utils/buffer.h
index f2bcba10..32a238b6 100644
--- a/src/vanillapdf/utils/buffer.h
+++ b/src/vanillapdf/utils/buffer.h
@@ -12,6 +12,7 @@
 #include <string>
 #include <ostream>
 #include <cassert>
+#include <cstring>
 
 namespace vanillapdf {