diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index ae6d62f..d0e5ba8 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -33,7 +33,7 @@
 #if defined(MBEDTLS_CTR_DRBG_C)
 
 #include "mbedtls/ctr_drbg.h"
-#include "mbedtls/utils.h"
+#include "mbedtls/platform_util.h"
 
 #include <string.h>
 
@@ -121,7 +121,7 @@
     mbedtls_mutex_free( &ctx->mutex );
 #endif
     mbedtls_aes_free( &ctx->aes_ctx );
-    mbedtls_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
+    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
 }
 
 void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx, int resistance )
@@ -241,16 +241,16 @@
     /*
     * tidy up the stack
     */
-    mbedtls_zeroize( buf, sizeof( buf ) );
-    mbedtls_zeroize( tmp, sizeof( tmp ) );
-    mbedtls_zeroize( key, sizeof( key ) );
-    mbedtls_zeroize( chain, sizeof( chain ) );
+    mbedtls_platform_zeroize( buf, sizeof( buf ) );
+    mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
+    mbedtls_platform_zeroize( key, sizeof( key ) );
+    mbedtls_platform_zeroize( chain, sizeof( chain ) );
     if( 0 != ret )
     {
         /*
         * wipe partial seed from memory
         */
-        mbedtls_zeroize( output, MBEDTLS_CTR_DRBG_SEEDLEN );
+        mbedtls_platform_zeroize( output, MBEDTLS_CTR_DRBG_SEEDLEN );
     }
 
     return( ret );
@@ -489,7 +489,7 @@
         ret = 0;
 
 exit:
-    mbedtls_zeroize( buf, sizeof( buf ) );
+    mbedtls_platform_zeroize( buf, sizeof( buf ) );
 
     fclose( f );
     return( ret );
@@ -522,7 +522,7 @@
 
     fclose( f );
 
-    mbedtls_zeroize( buf, sizeof( buf ) );
+    mbedtls_platform_zeroize( buf, sizeof( buf ) );
 
     if( ret != 0 )
         return( ret );