diff --git a/ArduPlane/altitude.pde b/ArduPlane/altitude.pde
index 71cb767b46..6f47d540b2 100644
--- a/ArduPlane/altitude.pde
+++ b/ArduPlane/altitude.pde
@@ -451,5 +451,7 @@ static float lookahead_adjustment(void)
 
     // constrain lookahead to a reasonable limit
     return constrain_float(lookahead, 0, 1000.0f);
+#else
+    return 0;
 #endif
 }