diff --git a/tests/scripts/test-ref-configs.pl b/tests/scripts/test-ref-configs.pl
index a434b46..5e11011 100755
--- a/tests/scripts/test-ref-configs.pl
+++ b/tests/scripts/test-ref-configs.pl
@@ -65,6 +65,7 @@
     print "\n******************************************\n";
     print "* Testing configuration: $conf\n";
     print "******************************************\n";
+    $ENV{MBEDTLS_TEST_CONFIGURATION} = "$conf";
 
     system( "cp configs/$conf $config_h" )
         and abort "Failed to activate $conf\n";