diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 1fd1d31..1e3c6fa 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -874,7 +874,7 @@
             mbedtls_md_type_t sig_md;
             {
                 int ret;
-                mbedtls_x509_crt_frame *frame;
+                mbedtls_x509_crt_frame const *frame;
                 ret = mbedtls_x509_crt_frame_acquire( cur->cert, &frame );
                 if( ret != 0 )
                     return( ret );
@@ -2996,7 +2996,7 @@
 
         while( crt != NULL && crt->raw.p != NULL )
         {
-            mbedtls_x509_crt_frame *frame;
+            mbedtls_x509_crt_frame const *frame;
             ret = mbedtls_x509_crt_frame_acquire( crt, &frame );
             if( ret != 0 )
                 return( ret );