diff --git a/src/shared/conf-parser.c b/src/shared/conf-parser.c
index 7bac3ead83..67c6aa792e 100644
--- a/src/shared/conf-parser.c
+++ b/src/shared/conf-parser.c
@@ -946,7 +946,7 @@ int config_parse_iec_uint64(
 
         r = parse_size(rvalue, 1024, bytes);
         if (r < 0)
-                log_syntax(unit, LOG_WARNING, filename, line, r, "Failed to parse size value, ignoring: %s", rvalue);
+                log_syntax(unit, LOG_WARNING, filename, line, r, "Failed to parse size value '%s', ignoring: %m", rvalue);
 
         return 0;
 }