diff --git a/src/encoder/basisu_enc.h b/src/encoder/basisu_enc.h
index 05656da..468f43b 100644
--- a/src/encoder/basisu_enc.h
+++ b/src/encoder/basisu_enc.h
@@ -22,6 +22,7 @@
 #include <functional>
 #include <thread>
 #include <unordered_map>
+#include <ostream>
 
 #ifndef _WIN32
 #include <libgen.h>
