diff --git a/firmware/baseband/clock_recovery.hpp b/firmware/baseband/clock_recovery.hpp
index 91f4cf8f..9a6904a3 100644
--- a/firmware/baseband/clock_recovery.hpp
+++ b/firmware/baseband/clock_recovery.hpp
@@ -168,7 +168,12 @@ private:
 	}
 
 	void symbol_callback(const float symbol, const float lateness) {
-		symbol_handler(symbol);
+		// NOTE: This check is to avoid std::function nullptr check, which
+		// brings in "_ZSt25__throw_bad_function_callv" and a lot of extra code.
+		// TODO: Make symbol_handler known at compile time.
+		if( symbol_handler) {
+			symbol_handler(symbol);
+		}
 
 		const float adjustment = error_filter(lateness);
 		resampler.advance(adjustment);
diff --git a/firmware/baseband/packet_builder.hpp b/firmware/baseband/packet_builder.hpp
index e3293529..c8a9ea5b 100644
--- a/firmware/baseband/packet_builder.hpp
+++ b/firmware/baseband/packet_builder.hpp
@@ -89,8 +89,13 @@ public:
 			}
 
 			if( end(bit_history, packet.size()) ) {
-				packet.set_timestamp(Timestamp::now());
-				payload_handler(packet);
+				// NOTE: This check is to avoid std::function nullptr check, which
+				// brings in "_ZSt25__throw_bad_function_callv" and a lot of extra code.
+				// TODO: Make payload_handler known at compile time.
+				if( payload_handler ) {
+					packet.set_timestamp(Timestamp::now());
+					payload_handler(packet);
+				}
 				reset_state();
 			} else {
 				if( packet_truncated() ) {