diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 58750c8b7..1336c7e4c 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -210,7 +210,7 @@ static int hmac_drbg_reseed_core( mbedtls_hmac_drbg_context *ctx,
     size_t seedlen = 0;
     size_t total_entropy_len;
     int ret = MBEDTLS_ERR_PLATFORM_FAULT_DETECTED;
-    volatile const unsigned char *additional_dup = additional;
+    const unsigned char * volatile additional_dup = additional;
     volatile size_t len_dup = len;
     int reseed_counter_backup = -1;
 
@@ -417,7 +417,7 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng,
     mbedtls_hmac_drbg_context *ctx = (mbedtls_hmac_drbg_context *) p_rng;
     size_t md_len = mbedtls_md_get_size(
         mbedtls_md_get_handle( &ctx->md_ctx ) );
-    size_t left = out_len;
+    volatile size_t left = out_len;
     unsigned char *out = output;
 
     /* II. Check request length */
@@ -430,8 +430,8 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng,
 
     /* 1. (aka VII and IX) Check reseed counter and PR */
     if( ctx->f_entropy != NULL && /* For no-reseeding instances */
-        ( ctx->prediction_resistance == MBEDTLS_HMAC_DRBG_PR_ON ||
-          ctx->reseed_counter > ctx->reseed_interval ) )
+            ( ctx->prediction_resistance == MBEDTLS_HMAC_DRBG_PR_ON ||
+              ctx->reseed_counter > ctx->reseed_interval ) )
     {
         if( ( ret = mbedtls_hmac_drbg_reseed( ctx, additional, add_len ) ) != 0 )
             return( ret );