diff --git a/src/game/mod.rs b/src/game/mod.rs
index 9e96fcd..4209df8 100644
--- a/src/game/mod.rs
+++ b/src/game/mod.rs
@@ -94,7 +94,7 @@ impl<'wl, WL: WordList> Game<'wl, WL> {
         for (idx, c) in guess.chars().enumerate() {
             if compare_solution.chars().nth(idx) == Some(c) {
                 status = Status::Matched;
-                compare_solution = compare_solution.replace(c, "_");
+                compare_solution.replace_range(idx..idx+1, "_");
             } else if compare_solution.contains(c) {
                 status = Status::Exists;
                 compare_solution = compare_solution.replacen(c, "_", 1);
diff --git a/src/solve/naive/mod.rs b/src/solve/naive/mod.rs
index 7cddb33..655efcf 100644
--- a/src/solve/naive/mod.rs
+++ b/src/solve/naive/mod.rs
@@ -35,7 +35,9 @@ impl<'wl, WL: WordList> Solver<'wl, WL> for NaiveSolver<'wl, WL> {
             .get_words_matching(pattern)
             .expect("the solution does not exist in the wordlist")
             .iter()
+            // only words that have not been guessed yet
             .filter(|p| !game.made_guesses().contains(&&p.0))
+            // only words that contain the letters we found earlier (that were not matched)
             .filter(|p| {
                 // TODO: don't repeat unmatched contained chars on the same position twice #2
                 let mut fits = true;