diff --git a/src/sensor_base.h b/src/sensor_base.h
index d65567b94a6338cacb5e681d0e8e229c8afe8b73..c3861a5020ade2d75eb9f1d8ac80489a32bfabf3 100644
--- a/src/sensor_base.h
+++ b/src/sensor_base.h
@@ -235,7 +235,7 @@ inline StateBlockPtr SensorBase::getStateBlockPtrStatic(unsigned int _i) const
 
 inline void SensorBase::setStateBlockPtrStatic(unsigned int _i, const StateBlockPtr _sb_ptr)
 {
-    assert((params_prior_map_.find(state_block_vec_[_i]) == params_prior_map_.end() || _sb_ptr == nullptr) && "overwriting a state block that has an absolute constraint");
+    assert((params_prior_map_.find(_i) == params_prior_map_.end() || _sb_ptr == nullptr) && "overwriting a state block that has an absolute constraint");
     state_block_vec_[_i] = _sb_ptr;
 }