diff --git a/src/logging/writers/ascii/Ascii.cc b/src/logging/writers/ascii/Ascii.cc
index fd73b4a9c2..f6f6c66e0e 100644
--- a/src/logging/writers/ascii/Ascii.cc
+++ b/src/logging/writers/ascii/Ascii.cc
@@ -122,10 +122,14 @@ TEST_CASE("writers.ascii prefix_basename_with")
 static std::optional<LeftoverLog> parse_shadow_log(const std::string& fname)
 	{
 	auto sfname = prefix_basename_with(fname, shadow_file_prefix);
+	string default_ext = "." + Ascii::LogExt();
+	if ( BifConst::LogAscii::gzip_level > 0 )
+		default_ext += ".gz";
 
 	LeftoverLog rval = {};
 	rval.filename = fname;
 	rval.shadow_filename = std::move(sfname);
+	rval.extension = default_ext;
 
 	auto sf_stream = fopen(rval.shadow_filename.data(), "r");
 
@@ -181,14 +185,16 @@ static std::optional<LeftoverLog> parse_shadow_log(const std::string& fname)
 
 	if ( sf_lines.size() < 2 )
 		{
-		rval.error = util::fmt("Found leftover log, '%s', but the associated shadow "
-		                       " file, '%s', required to process it is invalid",
-		                       rval.filename.data(), rval.shadow_filename.data());
-		return rval;
+		reporter->Warning("Found leftover log, '%s', but the associated shadow "
+		                  " file, '%s', required to process it is invalid: using default "
+		                  " for extension (%s) and post_proc_func",
+		                  rval.filename.data(), rval.shadow_filename.data(), default_ext.data());
+		}
+	else
+		{
+		rval.extension = sf_lines[0];
+		rval.post_proc_func = sf_lines[1];
 		}
-
-	rval.extension = sf_lines[0];
-	rval.post_proc_func = sf_lines[1];
 
 	struct stat st;