diff --git a/fantemp/controller.cpp b/fantemp/controller.cpp
index 46f02f2..015687b 100644
--- a/fantemp/controller.cpp
+++ b/fantemp/controller.cpp
@@ -7,6 +7,8 @@ double Controller::m_adcSample;
 double Controller::m_resistance;
 double Controller::m_temperature;
 uint8_t Controller::m_fanSpeed;
+bool Controller::m_dataAvailable = false;
+
 volatile uint32_t Controller::m_adcSampleSum;
 volatile bool Controller::m_adcSampleReady = false;
 
@@ -21,6 +23,7 @@ void Controller::callback()
 {
 	if (m_adcSampleReady) {
 		m_adcSample = static_cast<double>(m_adcSampleSum) / NUM_ADC_SAMPLES;
+		m_dataAvailable = true;
 		m_adcSampleReady = false;
 
 		m_resistance = m_thermistor.getResistance(m_adcSample);
diff --git a/fantemp/controller.hpp b/fantemp/controller.hpp
index bdd1de4..fd6d78b 100644
--- a/fantemp/controller.hpp
+++ b/fantemp/controller.hpp
@@ -12,6 +12,7 @@ class Controller {
 	static double m_resistance;
 	static double m_temperature;
 	static uint8_t m_fanSpeed;
+	static bool m_dataAvailable;
 
 	static void init();
 
diff --git a/fantemp/terminal.hpp b/fantemp/terminal.hpp
index f7c1e91..b5bad56 100644
--- a/fantemp/terminal.hpp
+++ b/fantemp/terminal.hpp
@@ -175,15 +175,19 @@ class Terminal {
 
 	static void showState()
 	{
-		char floatBuffer[16];
+		if (Controller::m_dataAvailable) {
+			char floatBuffer[16];
 
-		sprintf(floatBuffer, "%.2f", Controller::m_adcSample);
-		m_serial << F("ADC value ...: ") << floatBuffer << F(" / 1023") << detail::ENDL;
-		sprintf(floatBuffer, "%.2f", Controller::m_resistance);
-		m_serial << F("Resistance ..: ") << floatBuffer << F(" Ohm") << detail::ENDL;
-		sprintf(floatBuffer, "%.2f", Controller::m_temperature);
-		m_serial << F("Temperature .: ") << floatBuffer << F(" C") << detail::ENDL;
-		m_serial << F("Fan speed ...: ") << Controller::m_fanSpeed << F("%") << detail::ENDL;
+			sprintf(floatBuffer, "%.2f", Controller::m_adcSample);
+			m_serial << F("ADC value ...: ") << floatBuffer << F(" / 1023") << detail::ENDL;
+			sprintf(floatBuffer, "%.2f", Controller::m_resistance);
+			m_serial << F("Resistance ..: ") << floatBuffer << F(" Ohm") << detail::ENDL;
+			sprintf(floatBuffer, "%.2f", Controller::m_temperature);
+			m_serial << F("Temperature .: ") << floatBuffer << F(" C") << detail::ENDL;
+			m_serial << F("Fan speed ...: ") << Controller::m_fanSpeed << F("%") << detail::ENDL;
+		} else {
+			m_serial << F("No data available yet!") << detail::ENDL;
+		}
 	}
 
 	static void printCurve()