diff --git a/src/groveehr/groveehr.h b/src/groveehr/groveehr.h
index 94ac5b48..371fe83f 100644
--- a/src/groveehr/groveehr.h
+++ b/src/groveehr/groveehr.h
@@ -103,12 +103,6 @@ namespace upm {
      */
     uint32_t beatCounter();
 
-    /**
-     * Beat interrupt service routine (ISR)
-     *
-     */
-    static void beatISR(void *ctx);
-
     /**
      * Computes the heart rate
      *
@@ -117,6 +111,12 @@ namespace upm {
     int heartRate();
 
   private:
+    /**
+     * Beat interrupt service routine (ISR)
+     *
+     */
+    static void beatISR(void *ctx);
+    
     volatile uint32_t m_beatCounter;
     struct timeval m_startTime;
     mraa_gpio_context m_gpio;