diff --git a/host/chez/records.ss b/host/chez/records.ss
index 00b0a95..66fdc57 100644
--- a/host/chez/records.ss
+++ b/host/chez/records.ss
@@ -58,6 +58,14 @@
                  (find-method-any-protocol tag "valAt")
                  (find-method-any-protocol tag "cons"))))
        #t))
+;; a jrec that is map? — a record, or a deftype implementing clojure.lang
+;; .IPersistentMap (clojure.core.cache's caches do). `without` (dissoc) is the
+;; map-distinctive method: vectors/sets implement Associative/ILookup but not it.
+(define (jrec-maplike? x)
+  (and (jrec? x)
+       (or (jrec-record? x)
+           (find-method-any-protocol (jrec-tag x) "without"))
+       #t))
 (define jolt-deftype-kw (keyword "jolt" "deftype"))
 ;; unique present-vs-absent sentinel for extension-map lookups (so a present nil
 ;; in the extension map is distinguished from a genuine miss).
@@ -399,7 +407,7 @@
 ;; deftype is not. coll? additionally covers a deftype implementing a collection
 ;; interface. predicates.ss vars hold a snapshot, so re-def-var! after extending.
 (define %r-jolt-map? jolt-map?)
-(set! jolt-map? (lambda (x) (or (jrec-record? x) (%r-jolt-map? x))))
+(set! jolt-map? (lambda (x) (or (jrec-maplike? x) (%r-jolt-map? x))))
 (def-var! "clojure.core" "map?" jolt-map?)
 (def-var! "clojure.core" "coll?" (lambda (x) (or (jrec-collection? x) (jolt-coll-pred? x))))
 
diff --git a/test/chez/unit.edn b/test/chez/unit.edn
index cb1a1ec..5e85d49 100644
--- a/test/chez/unit.edn
+++ b/test/chez/unit.edn
@@ -563,4 +563,8 @@
   {:suite "bytes" :expr "(String. (byte-array [104 105]) \"UTF-8\")" :expected "hi"}
   {:suite "bytes" :expr "(int (first (String. (byte-array [200]) \"ISO-8859-1\")))" :expected "200"}
   {:suite "bytes" :expr "(String. (.getBytes \"round\" \"UTF-8\") \"UTF-8\")" :expected "round"}
+  {:suite "deftype-map" :expr "(do (deftype Mp [m] clojure.lang.IPersistentMap (without [_ k] m)) [(map? (->Mp 1)) (record? (->Mp 1))])" :expected "[true false]"}
+  {:suite "deftype-map" :expr "(do (deftype Op [s]) [(map? (->Op 1)) (record? (->Op 1)) (coll? (->Op 1))])" :expected "[false false false]"}
+  {:suite "deftype-map" :expr "(do (deftype Lc [xs] clojure.lang.Counted (count [_] (count xs)) clojure.lang.Seqable (seq [_] (seq xs))) [(coll? (->Lc [1 2])) (count (->Lc [1 2])) (vec (seq (->Lc [1 2])))])" :expected "[true 2 [1 2]]"}
+  {:suite "deftype-map" :expr "(do (defrecord Dr [a b]) [(map? (->Dr 1 2)) (record? (->Dr 1 2)) (coll? (->Dr 1 2))])" :expected "[true true true]"}
 ]