diff --git a/library/entropy.c b/library/entropy.c
index f68d68656..0d9a8150b 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -175,6 +175,8 @@ static int entropy_update( mbedtls_entropy_context *ctx, unsigned char source_id
     mbedtls_sha256_update( &ctx->accumulator, p, use_len );
 #endif
 
+    mbedtls_zeroize( tmp, sizeof( tmp ) );
+
     return( 0 );
 }