diff --git a/internal/codeguard/checks/quality/quality_clone.go b/internal/codeguard/checks/quality/quality_clone.go
index b6db576..30a73d6 100644
--- a/internal/codeguard/checks/quality/quality_clone.go
+++ b/internal/codeguard/checks/quality/quality_clone.go
@@ -97,6 +97,16 @@ const (
 // candidates are identical to the old per-window byte hashing.
 func cloneWindowIndex(docs []cloneDocument, threshold int) cloneIndex {
 	index := make(cloneIndex)
+	hasWindow := false
+	for _, doc := range docs {
+		if len(doc.Tokens) >= threshold {
+			hasWindow = true
+			break
+		}
+	}
+	if !hasWindow {
+		return index
+	}
 	// top = multiplier^(threshold-1), the weight of the token leaving the
 	// window on each slide.
 	top := uint64(1)
diff --git a/internal/codeguard/checks/quality/quality_clone_test.go b/internal/codeguard/checks/quality/quality_clone_test.go
index f10d4a6..230bdd2 100644
--- a/internal/codeguard/checks/quality/quality_clone_test.go
+++ b/internal/codeguard/checks/quality/quality_clone_test.go
@@ -16,3 +16,15 @@ func TestCollectCloneCandidatesCapsIdenticalDocuments(t *testing.T) {
 		t.Fatalf("candidate count = %d, want safety cap %d", len(candidates), maxCloneCandidates)
 	}
 }
+
+func TestCloneWindowIndexSkipsMultiplierForOversizedThreshold(t *testing.T) {
+	docs := []cloneDocument{
+		{Tokens: []cloneToken{{Hash: 1}}},
+		{Tokens: []cloneToken{{Hash: 1}}},
+	}
+	threshold := int(^uint(0) >> 1)
+
+	if index := cloneWindowIndex(docs, threshold); len(index) != 0 {
+		t.Fatalf("cloneWindowIndex() returned %d windows, want 0", len(index))
+	}
+}