diff --git a/src/lib-sieve/plugins/include/cmd-import.c b/src/lib-sieve/plugins/include/cmd-import.c
index 4ce10392d64a92f8d1ac64f5930ccfae47e330af..9f9f75b548cbbf1707cf426dfb54cad305ae899c 100644
--- a/src/lib-sieve/plugins/include/cmd-import.c
+++ b/src/lib-sieve/plugins/include/cmd-import.c
@@ -302,7 +302,8 @@ static int opc_import_execute
 		}
 		
 		if ( index >= var_count ) {
-			sieve_runtime_trace_error(renv, "invalid global variable index");
+			sieve_runtime_trace_error(renv, "invalid global variable index (%u > %u)",
+				index, var_count);
 			return SIEVE_EXEC_BIN_CORRUPT;
 		}