diff --git a/src/hmm/viterbi.rs b/src/hmm/viterbi.rs
index ba1efb2..57250da 100644
--- a/src/hmm/viterbi.rs
+++ b/src/hmm/viterbi.rs
@@ -63,6 +63,7 @@ impl<E: EmissionModel> HMM<E> {
 mod tests {
     use super::*;
     use crate::hmm::emission::GaussianEmission;
+    use crate::hmm::config::HMMConfig;
 
     #[test]
     fn test_viterbi() {