diff --git a/src/ecmult_impl.h b/src/ecmult_impl.h
index e6e5f471880..81ae08e100b 100644
--- a/src/ecmult_impl.h
+++ b/src/ecmult_impl.h
@@ -11,6 +11,8 @@
 #include "scalar.h"
 #include "ecmult.h"
 
+#include <string.h>
+
 /* optimal for 128-bit and 256-bit exponents. */
 #define WINDOW_A 5