diff --git a/src/uu/tr/src/operation.rs b/src/uu/tr/src/operation.rs
index 22fd890471..c6bdbfe227 100644
--- a/src/uu/tr/src/operation.rs
+++ b/src/uu/tr/src/operation.rs
@@ -386,8 +386,9 @@ impl Sequence {
             .collect();
 
         // For every upper/lower in set2, there must be an upper/lower in set1 at the same position. The position is calculated by expanding everything before the upper/lower in both sets
+        // With -c, set1 positions are those of the complement, so there is nothing to match.
         for (set2_pos, set2_item) in set2.iter().enumerate() {
-            if matches!(set2_item, Self::Class(_)) {
+            if !complement_flag && matches!(set2_item, Self::Class(_)) {
                 let set2_part_solved_len = Self::expanded_len_of(&set2[..set2_pos]);
 
                 let mut class_matches = false;
@@ -416,20 +417,6 @@ impl Sequence {
         let set2_uniques = Self::unique_chars(&set2_runs);
 
         let set1_has_class = set1.iter().any(|x| matches!(x, Self::Class(_)));
-        // If the complement flag is used in translate mode, only one unique
-        // character may appear in set2. Validate this with the set of uniques
-        // in set2 that we just generated.
-        // Also, set2 must not overgrow set1, otherwise the mapping can't be 1:1.
-        if set1_has_class
-            && translating
-            && complement_flag
-            && (set2_uniques.len() > 1 || set2_len > set1_len)
-        {
-            return Err(SequenceError::whole_set(
-                BadSequence::ComplementMoreThanOneUniqueInSet2,
-                2,
-            ));
-        }
 
         if set2_len < set1_len {
             if truncate_set1_flag {
@@ -460,6 +447,21 @@ impl Sequence {
             }
         }
 
+        // If the complement flag is used in translate mode, only one unique
+        // character may appear in set2. Validate this with the set of uniques
+        // in set2 that we just generated.
+        // Also, set2 must not overgrow set1, otherwise the mapping can't be 1:1.
+        if set1_has_class
+            && translating
+            && complement_flag
+            && (set2_uniques.len() > 1 || set2_len > set1_len)
+        {
+            return Err(SequenceError::whole_set(
+                BadSequence::ComplementMoreThanOneUniqueInSet2,
+                2,
+            ));
+        }
+
         // Line the two sets up position by position, one run at a time. A run
         // of one character in set1 maps that character to every character it
         // lines up with in set2, and the last mapping wins, so the pair at the
diff --git a/tests/by-util/test_tr.rs b/tests/by-util/test_tr.rs
index 2fd477dbf5..2bde3e176a 100644
--- a/tests/by-util/test_tr.rs
+++ b/tests/by-util/test_tr.rs
@@ -1047,6 +1047,64 @@ fn tr_translate_backslash_at_end() {
         .stderr_is("tr: warning: an unescaped backslash at end of string is not portable\n");
 }
 
+#[test]
+fn test_complement_set1_longer_than_set2_ending_in_class() {
+    let msg = "tr: when translating with string1 longer than string2,\nthe latter string must not end with a character class\n";
+    for (flags, set1, set2) in [
+        ("-c", "[:upper:]", "[:lower:]"),
+        ("-c", "[:lower:]", "[:upper:]"),
+        ("-c", "[:upper:]", "x[:lower:]"),
+        ("-c", "[:digit:]", "[:upper:]"),
+        ("-c", "[:upper:]", "[:upper:]"),
+        ("-c", "a-z", "[:upper:]"),
+        ("-c", "a", "[:upper:]"),
+        ("-cs", "[:upper:]", "[:lower:]"),
+    ] {
+        new_ucmd!()
+            .args(&[flags, set1, set2])
+            .pipe_in("AbC1z\n")
+            .fails_with_code(1)
+            .stderr_only(msg);
+    }
+}
+
+#[test]
+fn test_complement_class_in_set2_without_class_in_set1() {
+    // The complement of everything is empty, so nothing is translated.
+    new_ucmd!()
+        .args(&["-c", "\\000-\\377", "[:upper:]"])
+        .pipe_in("AbC1z\n")
+        .succeeds()
+        .stdout_only("AbC1z\n");
+
+    new_ucmd!()
+        .args(&["-c", "\\000-\\375", "[:upper:]"])
+        .pipe_in(b"\xfe\xffAa\n".as_slice())
+        .succeeds()
+        .stdout_only("ABAa\n");
+
+    new_ucmd!()
+        .args(&["-c", "a-z", "[:upper:]x"])
+        .pipe_in("AbC1z\n")
+        .succeeds()
+        .stdout_only("xbxxzK");
+}
+
+#[test]
+fn test_complement_class_in_set2_unique_chars_error() {
+    let msg = "tr: when translating with complemented character classes,\nstring2 must map all characters in the domain to one\n";
+    for (flags, set1, set2) in [
+        ("-c", "[:upper:]", "[:lower:]x"),
+        ("-ct", "[:upper:]", "[:lower:]"),
+    ] {
+        new_ucmd!()
+            .args(&[flags, set1, set2])
+            .pipe_in("AbC1z\n")
+            .fails_with_code(1)
+            .stderr_only(msg);
+    }
+}
+
 #[test]
 fn tr_ross_delete_no_squeeze() {
     // # From Ross