diff --git a/libraries/AP_IMU/AP_IMU.cpp b/libraries/AP_IMU/AP_IMU.cpp
index 81e797b0d0..6f49396b85 100644
--- a/libraries/AP_IMU/AP_IMU.cpp
+++ b/libraries/AP_IMU/AP_IMU.cpp
@@ -54,7 +54,8 @@ const float   AP_IMU::_gyro_temp_curve[3][3] = {
 	{1665,0,0}
 };	// To Do - make additional constructors to pass this in.
 
-
+// Someone is responsible for providing an APM_ADC instance.
+extern APM_ADC_Class	APM_ADC;
 
 // Constructors ////////////////////////////////////////////////////////////////
 
diff --git a/libraries/AP_IMU/AP_IMU.h b/libraries/AP_IMU/AP_IMU.h
index 682f629f66..6ea880a4d7 100644
--- a/libraries/AP_IMU/AP_IMU.h
+++ b/libraries/AP_IMU/AP_IMU.h
@@ -46,5 +46,3 @@ private:
 };
 
 #endif
-
-