diff --git a/include/sonar.h b/include/sonar.h
index 03a1199..ff2a32f 100644
--- a/include/sonar.h
+++ b/include/sonar.h
@@ -40,6 +40,6 @@
 
 void init_sonar(void);
 void trigger_sonar(void);
-unsigned int read_sonar(void);
+int read_sonar(void);
 
 #endif /* SONAR_H */
diff --git a/src/sonar.c b/src/sonar.c
index 4f15e14..fb780ce 100644
--- a/src/sonar.c
+++ b/src/sonar.c
@@ -28,7 +28,7 @@ ISR(TIMER1_OVF_vect)
     TCNT1 = 0;
 }
 
-unsigned int read_sonar()
+int read_sonar()
 {
     int dist_in_cm = 0;
     init_sonar();