diff --git a/model/labels/regexp.go b/model/labels/regexp.go
index de4cfc3b1c..e6909dbeac 100644
--- a/model/labels/regexp.go
+++ b/model/labels/regexp.go
@@ -366,7 +366,7 @@ func optimizeAlternatingLiterals(s string) (StringMatcher, []string) {
 	// If there are no alternates, check if the string is a literal
 	if estimatedAlternates == 1 {
 		if regexp.QuoteMeta(s) == s {
-			return &equalStringMatcher{s: s, caseSensitive: true}, nil
+			return &equalStringMatcher{s: s, caseSensitive: true}, []string{s}
 		}
 		return nil, nil
 	}
diff --git a/model/labels/regexp_test.go b/model/labels/regexp_test.go
index f0e21b2d5c..a03bbd261d 100644
--- a/model/labels/regexp_test.go
+++ b/model/labels/regexp_test.go
@@ -342,6 +342,14 @@ func TestFindSetMatches(t *testing.T) {
 			matches, actualCaseSensitive := findSetMatches(parsed)
 			require.Equal(t, c.expMatches, matches)
 			require.Equal(t, c.expCaseSensitive, actualCaseSensitive)
+
+			if c.expCaseSensitive {
+				// When the regexp is case sensitive, we want to ensure that the
+				// set matches are maintained in the final matcher.
+				r, err := newFastRegexMatcherWithoutCache(c.pattern)
+				require.NoError(t, err)
+				require.Equal(t, c.expMatches, r.SetMatches())
+			}
 		})
 	}
 }