diff --git a/include/IMU/processor/processor_IMU.h b/include/IMU/processor/processor_IMU.h
index 4204b264a915e07a384720e6716139c9cf5bba9b..61c725e56bc04d5503703c610e44e17f6d6c8800 100644
--- a/include/IMU/processor/processor_IMU.h
+++ b/include/IMU/processor/processor_IMU.h
@@ -61,7 +61,7 @@ class ProcessorIMU : public ProcessorMotion{
                                 const Scalar _dt,
                                 Eigen::VectorXs& _x_plus_delta ) const override;
         virtual Eigen::VectorXs deltaZero() const override;
-        virtual bool voteForKeyFrame() override;
+        virtual bool voteForKeyFrame() const override;
         virtual CaptureMotionPtr emplaceCapture(const FrameBasePtr& _frame_own,
                                                 const SensorBasePtr& _sensor,
                                                 const TimeStamp& _ts,
diff --git a/src/processor/processor_IMU.cpp b/src/processor/processor_IMU.cpp
index c8342b1266ee0172e5ace5b2c68771bb7c7e4e99..5e85be73eff3835395529a132b63e351dedfb7fe 100644
--- a/src/processor/processor_IMU.cpp
+++ b/src/processor/processor_IMU.cpp
@@ -32,7 +32,7 @@ ProcessorBasePtr ProcessorIMU::create(const std::string& _unique_name, const Pro
     return prc_ptr;
 }
 
-bool ProcessorIMU::voteForKeyFrame()
+bool ProcessorIMU::voteForKeyFrame() const
 {
     // time span
     if (getBuffer().get().back().ts_ - getBuffer().get().front().ts_ > params_motion_IMU_->max_time_span)