diff --git a/src/problem.cpp b/src/problem.cpp
index 63775a5ad6fedd519e993604ea745679c37a3f2d..609f85a25b484bef7b7104fcb62dbafe6dca4a2b 100644
--- a/src/problem.cpp
+++ b/src/problem.cpp
@@ -330,11 +330,18 @@ bool Problem::permitKeyFrame(ProcessorBasePtr _processor_ptr)
 
 void Problem::keyFrameCallback(FrameBasePtr _keyframe_ptr, ProcessorBasePtr _processor_ptr, const Scalar& _time_tolerance)
 {
-    WOLF_DEBUG((_processor_ptr->isMotion() ? "PM " : "PT "), _processor_ptr->getName(), ": KF", _keyframe_ptr->id(), " Callback emitted with ts = ", _keyframe_ptr->getTimeStamp());
+    if (_processor_ptr)
+    {
+        WOLF_DEBUG((_processor_ptr->isMotion() ? "PM " : "PT "), _processor_ptr->getName(), ": KF", _keyframe_ptr->id(), " Callback emitted with ts = ", _keyframe_ptr->getTimeStamp());
+    }
+    else
+    {
+        WOLF_DEBUG("External callback: KF", _keyframe_ptr->id(), " Callback emitted with ts = ", _keyframe_ptr->getTimeStamp());
+    }
 
     for (auto sensor : hardware_ptr_->getSensorList())
-    	for (auto processor : sensor->getProcessorList())
-    		if (processor && (processor != _processor_ptr) )
+        for (auto processor : sensor->getProcessorList())
+            if (processor && (processor != _processor_ptr) )
                 processor->keyFrameCallback(_keyframe_ptr, _time_tolerance);
 }
 
diff --git a/src/test/gtest_IMU.cpp b/src/test/gtest_IMU.cpp
index ea51761bbf8d1f59d06cdff71923fc686c302fbd..5c5f48204e39cb1e42f71517fb89cddcf948f561 100644
--- a/src/test/gtest_IMU.cpp
+++ b/src/test/gtest_IMU.cpp
@@ -503,11 +503,9 @@ class Process_Constraint_IMU : public testing::Test
             FrameBasePtr KF = problem->emplaceFrame(KEY_FRAME, x1_exact, t);
 
             // ===================================== IMU CALLBACK
-            processor_imu->keyFrameCallback(KF, dt/2);
-
-
-
+            problem->keyFrameCallback(KF, nullptr, dt/2);
 
+            // Process IMU for the callback to take effect
             data = Vector6s::Zero();
             capture_imu = make_shared<CaptureIMU>(t+dt, sensor_imu, data, sensor_imu->getNoiseCov());
             processor_imu->process(capture_imu);
@@ -685,8 +683,7 @@ class Process_Constraint_IMU_ODO : public Process_Constraint_IMU
             Process_Constraint_IMU::buildProblem();
 
             // ===================================== ODO
-            processor_odo->keyFrameCallback(KF_1, 0.1);
-
+            // Process ODO for the callback to take effect
             data = Vector6s::Zero();
             capture_odo = make_shared<CaptureOdom3D>(t+dt, sensor_odo, data, sensor_odo->getNoiseCov());
             processor_odo->process(capture_odo);
@@ -1540,7 +1537,7 @@ int main(int argc, char **argv)
     testing::InitGoogleTest(&argc, argv);
     //    ::testing::GTEST_FLAG(filter) = "Process_Constraint_IMU.*";
     //    ::testing::GTEST_FLAG(filter) = "Process_Constraint_IMU_ODO.*";
-    //    ::testing::GTEST_FLAG(filter) = "Process_Constraint_IMU_ODO.RecoverTrajectory_MotionRandom_PqV_b__pqV_b";
+        ::testing::GTEST_FLAG(filter) = "Process_Constraint_IMU_ODO.RecoverTrajectory_MotionRandom_PqV_b__pqV_b";
 
     return RUN_ALL_TESTS();
 }