diff --git a/host/chez/seq.ss b/host/chez/seq.ss
index 96e3899..b924cc2 100644
--- a/host/chez/seq.ss
+++ b/host/chez/seq.ss
@@ -162,19 +162,30 @@
 (define unc-mask64 #xFFFFFFFFFFFFFFFF)
 (define unc-2^63   #x8000000000000000)
 (define unc-2^64   #x10000000000000000)
+(define unc-neg-2^63 (- unc-2^63))
+;; Wrap to a signed 64-bit value. Fast path: an exact integer already in
+;; [-2^63, 2^63) is its own wrap — skip the bignum mask, which on Chez (61-bit
+;; fixnums) allocates for any value past 2^60. Only an out-of-range result (a
+;; multiply overflowing into 128 bits) needs the mask + sign fixup.
 (define (jolt-wrap64 x)
-  (let ((m (bitwise-and (if (and (number? x) (exact? x) (integer? x)) x (exact (floor x))) unc-mask64)))
-    (if (>= m unc-2^63) (- m unc-2^64) m)))
-;; unchecked-* only WRAP integer (long) math; on a flonum operand they are an
-;; ordinary float op, since *unchecked-math* never wraps doubles — Clojure:
-;; (unchecked-multiply 1.5 2.0) => 3.0, not a truncated long. (test.check's
-;; rand-double is (* double-unit shifted) under *unchecked-math*.)
-(define (jolt-uncadd2 a b) (if (or (flonum? a) (flonum? b)) (+ a b) (jolt-wrap64 (+ a b))))
-(define (jolt-uncsub2 a b) (if (or (flonum? a) (flonum? b)) (- a b) (jolt-wrap64 (- a b))))
-(define (jolt-uncmul2 a b) (if (or (flonum? a) (flonum? b)) (* a b) (jolt-wrap64 (* a b))))
-(define (jolt-uncinc x)    (if (flonum? x) (+ x 1.0) (jolt-wrap64 (+ x 1))))
-(define (jolt-uncdec x)    (if (flonum? x) (- x 1.0) (jolt-wrap64 (- x 1))))
-(define (jolt-uncneg x)    (if (flonum? x) (- x) (jolt-wrap64 (- x))))
+  (if (and (exact? x) (integer? x) (>= x unc-neg-2^63) (< x unc-2^63))
+      x
+      (let ((m (bitwise-and (if (and (number? x) (exact? x) (integer? x)) x (exact (floor x))) unc-mask64)))
+        (if (>= m unc-2^63) (- m unc-2^64) m))))
+;; unchecked-* only WRAP integer (long) math; on a flonum OR ratio operand they
+;; are an ordinary numeric op, since *unchecked-math* never wraps a non-long —
+;; Clojure's unchecked-add falls back to regular arithmetic for non-primitives:
+;; (unchecked-multiply 1.5 2.0) => 3.0, (unchecked-add 2/3 2/3) => 4/3, not a
+;; truncated long. (test.check's rand-double is (* double-unit shifted), and
+;; gen/ratio sums ratios, both under *unchecked-math*.) Wrap iff both are exact
+;; integers.
+(define (unc-int? x) (and (exact? x) (integer? x)))
+(define (jolt-uncadd2 a b) (if (and (unc-int? a) (unc-int? b)) (jolt-wrap64 (+ a b)) (+ a b)))
+(define (jolt-uncsub2 a b) (if (and (unc-int? a) (unc-int? b)) (jolt-wrap64 (- a b)) (- a b)))
+(define (jolt-uncmul2 a b) (if (and (unc-int? a) (unc-int? b)) (jolt-wrap64 (* a b)) (* a b)))
+(define (jolt-uncinc x)    (if (unc-int? x) (jolt-wrap64 (+ x 1)) (+ x 1)))
+(define (jolt-uncdec x)    (if (unc-int? x) (jolt-wrap64 (- x 1)) (- x 1)))
+(define (jolt-uncneg x)    (if (unc-int? x) (jolt-wrap64 (- x)) (- x)))
 (define (jolt-unchecked-add . xs) (if (null? xs) 0 (fold-left jolt-uncadd2 (car xs) (cdr xs))))
 (define (jolt-unchecked-mul . xs) (if (null? xs) 1 (fold-left jolt-uncmul2 (car xs) (cdr xs))))
 (define (jolt-unchecked-sub . xs)
diff --git a/test/chez/corpus.edn b/test/chez/corpus.edn
index c1524b6..0616755 100644
--- a/test/chez/corpus.edn
+++ b/test/chez/corpus.edn
@@ -1484,6 +1484,11 @@
   {:suite "numbers / promoting & unchecked aliases" :label "unchecked-remainder-int negative" :expected "-1" :actual "(unchecked-remainder-int -7 2)"}
   {:suite "numbers / promoting & unchecked aliases" :label "unchecked-int truncates" :expected "3" :actual "(unchecked-int 3.7)"}
   {:suite "numbers / promoting & unchecked aliases" :label "unchecked-int negative" :expected "-3" :actual "(unchecked-int -3.7)"}
+  {:suite "numbers / promoting & unchecked aliases" :label "unchecked-add on ratios does not wrap to long" :expected "4/3" :actual "(unchecked-add 2/3 2/3)"}
+  {:suite "numbers / promoting & unchecked aliases" :label "unchecked-multiply ratio by int" :expected "4/3" :actual "(unchecked-multiply 2/3 2)"}
+  {:suite "numbers / promoting & unchecked aliases" :label "unchecked-negate ratio" :expected "-2/3" :actual "(unchecked-negate 2/3)"}
+  {:suite "numbers / promoting & unchecked aliases" :label "unchecked-add ratios summing to zero" :expected "0" :actual "(unchecked-add 1/2 -1/2)"}
+  {:suite "numbers / promoting & unchecked aliases" :label "unchecked-inc ratio" :expected "3/2" :actual "(unchecked-inc 1/2)"}
   {:suite "numbers / promoting & unchecked aliases" :label "unchecked-long" :expected "3" :actual "(unchecked-long 3.7)"}
   {:suite "numbers / promoting & unchecked aliases" :label "int? on integer" :expected "true" :actual "(int? 5)"}
   {:suite "numbers / promoting & unchecked aliases" :label "int? on double" :expected "false" :actual "(int? 5.5)"}