diff --git a/aos/events/logging/logfile_sorting.cc b/aos/events/logging/logfile_sorting.cc
index b8530fb..f67a88a 100644
--- a/aos/events/logging/logfile_sorting.cc
+++ b/aos/events/logging/logfile_sorting.cc
@@ -2085,6 +2085,14 @@
   return sorter.SortParts();
 }
 
+std::set<std::string> LoggerNodes(const std::vector<LogFile> &log_files) {
+  std::set<std::string> nodes;
+  for (const aos::logger::LogFile &log : log_files) {
+    nodes.insert(log.logger_node);
+  }
+  return nodes;
+}
+
 std::ostream &operator<<(std::ostream &stream, const LogFile &file) {
   stream << "{\n";
   if (!file.log_event_uuid.empty()) {
diff --git a/aos/events/logging/logfile_sorting.h b/aos/events/logging/logfile_sorting.h
index e1aa620..825a210 100644
--- a/aos/events/logging/logfile_sorting.h
+++ b/aos/events/logging/logfile_sorting.h
@@ -150,6 +150,10 @@
 // Sort parts of a single log.
 std::vector<LogFile> SortParts(const LogSource &log_source);
 
+// Returns a list of all the logger nodes for the specified set of log files.
+// For single-node systems, the empty string will represent the logfile set.
+std::set<std::string> LoggerNodes(const std::vector<LogFile> &log_files);
+
 // Validates that collection of log files or log parts shares the same configs.
 bool HasMatchingConfigs(const std::vector<LogFile> &items);
 
diff --git a/aos/util/log_to_mcap.cc b/aos/util/log_to_mcap.cc
index 0d51e52..d0a2415 100644
--- a/aos/util/log_to_mcap.cc
+++ b/aos/util/log_to_mcap.cc
@@ -37,19 +37,19 @@
   const std::vector<aos::logger::LogFile> logfiles =
       aos::logger::SortParts(aos::logger::FindLogs(argc, argv));
   CHECK(!logfiles.empty());
-  const std::string logger_node = logfiles.at(0).logger_node;
-  bool all_logs_from_same_node = true;
-  for (const aos::logger::LogFile &log : logfiles) {
-    if (log.logger_node != logger_node) {
-      all_logs_from_same_node = false;
-      break;
-    }
-  }
+  const std::set<std::string> logger_nodes = aos::logger::LoggerNodes(logfiles);
+  CHECK_LT(0u, logger_nodes.size());
+  const std::string logger_node = *logger_nodes.begin();
   std::string replay_node = FLAGS_node;
-  if (replay_node.empty() && all_logs_from_same_node) {
-    LOG(INFO) << "Guessing \"" << logger_node
-              << "\" as node given that --node was not specified.";
-    replay_node = logger_node;
+  if (replay_node.empty()) {
+    if (logger_nodes.size() == 1u) {
+      LOG(INFO) << "Guessing \"" << logger_node
+                << "\" as node given that --node was not specified.";
+      replay_node = logger_node;
+    } else {
+      LOG(ERROR) << "Must supply a --node for log_to_mcap.";
+      return 1;
+    }
   }
 
   std::optional<aos::FlatbufferDetachedBuffer<aos::Configuration>> config;