diff --git a/include/mbedtls/entropy.h b/include/mbedtls/entropy.h
index 747aca4..addb961 100644
--- a/include/mbedtls/entropy.h
+++ b/include/mbedtls/entropy.h
@@ -121,6 +121,7 @@
  */
 typedef struct
 {
+    int accumulator_started;
 #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
     mbedtls_sha512_context  accumulator;
 #else