diff --git a/include/mbedtls/bignum.h b/include/mbedtls/bignum.h
index 931e06d2c3..87520726cc 100644
--- a/include/mbedtls/bignum.h
+++ b/include/mbedtls/bignum.h
@@ -59,7 +59,7 @@
  *
  * Reduction in size, reduces speed.
  */
-#define MBEDTLS_MPI_WINDOW_SIZE                           2        /**< Maximum window size used. */
+#define MBEDTLS_MPI_WINDOW_SIZE                           3        /**< Maximum window size used. */
 #endif /* !MBEDTLS_MPI_WINDOW_SIZE */
 
 #if !defined(MBEDTLS_MPI_MAX_SIZE)