diff --git a/include/geos/shape/fractal/HilbertEncoder.h b/include/geos/shape/fractal/HilbertEncoder.h
index 61c0010d4..eba5bba8f 100644
--- a/include/geos/shape/fractal/HilbertEncoder.h
+++ b/include/geos/shape/fractal/HilbertEncoder.h
@@ -18,6 +18,7 @@
 #include <geos/export.h>
 #include <string>
 #include <vector>
+#include <cstdint>
 
 // Forward declarations
 namespace geos {