diff --git a/Cargo.toml b/Cargo.toml
index 4a6ab90..9b1753a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@
 
 [package]
 name = "wellen"
-version = "0.9.5"
+version = "0.9.6"
 edition = "2021"
 authors = ["Kevin Laeufer <laeufer@berkeley.edu>"]
 description = "Fast VCD and FST library for waveform viewers written in Rust."
@@ -33,6 +33,7 @@ vcd = "0.7.0"
 clap = { version = "4.4.6", features = ["derive"] }
 criterion = "0.5"
 indicatif = "0.17.8"
+proptest = "1.4.0"
 
 [profile.release]
 debug = true
diff --git a/src/ghw/hierarchy.rs b/src/ghw/hierarchy.rs
index 62ee614..90bccf6 100644
--- a/src/ghw/hierarchy.rs
+++ b/src/ghw/hierarchy.rs
@@ -1378,9 +1378,3 @@ impl FloatRange {
         self_range.start() >= other_range.start() && self_range.end() <= other_range.end()
     }
 }
-
-#[derive(Debug, Copy, Clone, PartialEq)]
-struct GhwUnit {
-    name: StringId,
-    value: i64,
-}
diff --git a/src/ghw/signals.rs b/src/ghw/signals.rs
index 109eb52..be09091 100644
--- a/src/ghw/signals.rs
+++ b/src/ghw/signals.rs
@@ -362,8 +362,7 @@ impl VecBuffer {
         // note, we keep the signal on the change list
 
         // return reference to value
-        let data = &self.data[info.data_range()];
-        data
+        &self.data[info.data_range()]
     }
 
     #[inline]
diff --git a/src/wavemem.rs b/src/wavemem.rs
index 0204e87..f7b7ea5 100644
--- a/src/wavemem.rs
+++ b/src/wavemem.rs
@@ -1005,8 +1005,9 @@ fn compress_template(
 ) {
     debug_assert!(in_states.bits_in_a_byte() < out_states.bits_in_a_byte());
     let mut working_byte = 0u8;
+    let max_bits = value.len() * in_states.bits_in_a_byte();
     for bit in (0..bits).rev() {
-        let rev_bit = bits - bit - 1;
+        let rev_bit = max_bits - bit - 1;
         let in_byte = value[rev_bit / in_states.bits_in_a_byte()];
         let in_value =
             (in_byte >> ((bit % in_states.bits_in_a_byte()) * in_states.bits())) & in_states.mask();
@@ -1180,4 +1181,37 @@ mod tests {
             }
         }
     }
+
+    use proptest::prelude::*;
+
+    fn convert_to_bits(states: States, chars: &str) -> Vec<u8> {
+        let mut out = Vec::new();
+        write_n_state(states, chars.as_bytes(), &mut out, None);
+        out
+    }
+
+    fn do_test_compress(value: String, max_states: States) {
+        let min_states = check_states(value.as_bytes()).unwrap();
+        let bits = value.len();
+        // convert string to bit vector
+        let max_value = convert_to_bits(max_states, &value);
+        // compress
+        let mut out = Vec::new();
+        compress(&max_value, max_states, min_states, bits, &mut out);
+        // check
+        let direct_conversion = convert_to_bits(min_states, &value);
+        assert_eq!(direct_conversion, out, "{value} - write_n_states -> {max_value:?} - compress -> {out:?} != {direct_conversion:?}");
+    }
+
+    proptest! {
+        #[test]
+        fn compress_from_nine_state(value in "[01xz]{0,4}") {
+            do_test_compress(value, States::Nine);
+        }
+
+        #[test]
+        fn compress_from_four_state(value in "[01]{0,4}") {
+            do_test_compress(value, States::Four);
+        }
+    }
 }