diff --git a/opendbc/can/common.h b/opendbc/can/common.h
index 77d2a73dd9..b79bae6aad 100644
--- a/opendbc/can/common.h
+++ b/opendbc/can/common.h
@@ -83,6 +83,7 @@ class CANParser {
   std::set<uint32_t> update(const std::vector<CanData> &can_data);
 
 protected:
+  void clearAllValues();
   void updateCans(const CanData &can, std::set<uint32_t> &updated_addresses);
   void UpdateValid(uint64_t nanos);
 };
diff --git a/opendbc/can/parser.cc b/opendbc/can/parser.cc
index db109965ad..cf19bc4cad 100644
--- a/opendbc/can/parser.cc
+++ b/opendbc/can/parser.cc
@@ -158,25 +158,34 @@ CANParser::CANParser(int abus, const std::string& dbc_name, bool ignore_checksum
 }
 
 std::set<uint32_t> CANParser::update(const std::vector<CanData> &can_data) {
-  // Clear all_vals in message_states
-  for (auto &[_, state] : message_states) {
-    for (auto &vals : state.all_vals) {
-      vals.clear();
-    }
+  clearAllValues();
+  std::set<uint32_t> updated_addresses;
+
+  if (can_data.empty()) {
+    return updated_addresses;
+  }
+
+  if (first_nanos == 0) {
+    first_nanos = can_data.front().nanos;
   }
 
-  std::set<uint32_t> updated_addresses;
   for (const auto &c : can_data) {
-    if (first_nanos == 0) {
-      first_nanos = c.nanos;
-    }
     last_nanos = std::max(last_nanos, c.nanos);
     updateCans(c, updated_addresses);
     UpdateValid(last_nanos);
   }
+
   return updated_addresses;
 }
 
+void CANParser::clearAllValues() {
+  for (auto &[_, state] : message_states) {
+    for (auto &vals : state.all_vals) {
+      vals.clear();
+    }
+  }
+}
+
 void CANParser::updateCans(const CanData &can, std::set<uint32_t> &updated_addresses) {
   //DEBUG("got %zu messages\n", can.frames.size());