diff --git a/RadarKit/CDXRadar.h b/RadarKit/CDXRadar.h
index 8a8d8f7..f28e390 100644
--- a/RadarKit/CDXRadar.h
+++ b/RadarKit/CDXRadar.h
@@ -45,7 +45,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  *  @param handler Block of code to execute when the Radar session has finished.
  */
--(CDXRadarSession *)runInBackgroundWithCompletionHandler:(nonnull void(^)(NSError *error))handler;
+-(CDXRadarSession *)runInBackgroundWithCompletionHandler:(nonnull void(^)(NSError * _Nullable error))handler;
 
 @end
-NS_ASSUME_NONNULL_END
\ No newline at end of file
+NS_ASSUME_NONNULL_END