diff --git a/src/sensorinterface/i2cimpl.h b/src/sensorinterface/i2cimpl.h
index 14e258c..032c240 100644
--- a/src/sensorinterface/i2cimpl.h
+++ b/src/sensorinterface/i2cimpl.h
@@ -82,7 +82,9 @@ struct I2CImpl : public RegisterInterface {
 	uint8_t getAddress() const override { return m_devAddr; }
 
 	std::string toString() const {
-		return std::string("I2C(") + std::to_string(m_devAddr) + std::string(")");
+		char buf[16];
+		std::snprintf(buf, sizeof(buf), "I2C(0x%02x)", m_devAddr);
+		return std::string(buf);
 	}
 
 private:
diff --git a/src/sensors/SensorBuilder.h b/src/sensors/SensorBuilder.h
index e2730ab..5bed41d 100644
--- a/src/sensors/SensorBuilder.h
+++ b/src/sensors/SensorBuilder.h
@@ -269,7 +269,7 @@ public:
 				}
 			);
 		} else {
-			auto& regInterface = getRegisterInterface<SensorType>(
+			auto& regInterface = *getRegisterInterface<SensorType>(
 				sensorID,
 				sensorInterface,
 				accessInterface
@@ -303,7 +303,7 @@ public:
 			sensorDef.imuInterface.toString().c_str(),
 			sensorDef.rotation,
 			sensorDef.sensorInterface->toString().c_str(),
-			sensorDef.intPin->toString().c_str(),
+			sensorDef.intPin ? sensorDef.intPin->toString().c_str() : "None",
 			sensorDef.extraParam,
 			sensorDef.optional
 		);