diff --git a/library/ecp.c b/library/ecp.c
index d3e42a9..fa91b3e 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3156,7 +3156,7 @@
 cleanup:
 
     if( ret < 0 && verbose != 0 )
-        mbedtls_printf( "Unexpected error, return code = %08X\n", ret );
+        mbedtls_printf( "Unexpected error, return code = %08X\n", (unsigned int) ret );
 
     mbedtls_ecp_group_free( &grp );
     mbedtls_ecp_point_free( &R );