diff --git a/Changes.md b/Changes.md
index 7f9ff32..df05304 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,3 +1,8 @@
+## 0.1.3
+
+- When sorting a file with repeated lines with a `--locale`, the sorting order was not always
+  consistent, and the `--unique` flag could leave duplicates behind.
+
 ## 0.1.2 - 2023-06-04
 
 - Sorting is now done in parallel using [rayon](https://docs.rs/rayon/latest/rayon/). This
diff --git a/src/comparer.rs b/src/comparer.rs
index 56bd28a..2e697c2 100644
--- a/src/comparer.rs
+++ b/src/comparer.rs
@@ -444,7 +444,16 @@ fn compare_two_strings(
     str2: &str,
 ) -> Ordering {
     if let Some(c) = collator {
-        c.compare(str1, str2)
+        let ord = c.compare(str1, str2);
+        if ord != Ordering::Equal {
+            return ord;
+        }
+        // If the strings are equal according to the collator they may still
+        // be different, in which case we want to further sort them
+        // somehow. Otherwise they end up sorted based on their original order
+        // in the file, which is random and means two files containing the
+        // same lines in different order could be sorted differently.
+        str1.cmp(str2)
     } else if case_insensitive {
         str1.to_lowercase().cmp(&str2.to_lowercase())
     } else {
diff --git a/src/test-cases/locale-not-unique.test b/src/test-cases/locale-not-unique.test
new file mode 100644
index 0000000..e342b90
--- /dev/null
+++ b/src/test-cases/locale-not-unique.test
@@ -0,0 +1,14 @@
+--sort text --case-insensitive --locale en-US --unique
+####
+NotSorted
+####
+ª
+A
+a
+ª
+A
+a
+####
+A
+a
+ª