diff --git a/racket/src/expander/common/module-path.rkt b/racket/src/expander/common/module-path.rkt
index 808e1594bf..010dc0da1b 100644
--- a/racket/src/expander/common/module-path.rkt
+++ b/racket/src/expander/common/module-path.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 (require racket/private/place-local
          ffi/unsafe/atomic
+         racket/fixnum
          "../compile/serialize-property.rkt"
          "../common/performance.rkt"
          "contract.rkt"
@@ -190,6 +191,8 @@
        (fprintf port "=~a" (module-path-index-resolved r))])
     (write-string ">" port)))
 
+(define empty-shift-cache '())
+
 ;; Serialization of a module path index is handled specially, because they
 ;; must be shared across phases of a module
 (define deserialize-module-path-index
@@ -259,7 +262,7 @@
          [(and (pair? mod-path) (eq? 'submod (car mod-path)))
           (loop (cadr mod-path))]
          [else base])))
-    (module-path-index mod-path keep-base #f #f)]))
+    (module-path-index mod-path keep-base #f empty-shift-cache)]))
 
 (define (module-path-index-resolve/maybe base load?)
   (if (module-path-index? base)
@@ -282,7 +285,7 @@
 
 (define make-self-module-path-index
   (case-lambda
-    [(name) (module-path-index #f #f name #f)]
+    [(name) (module-path-index #f #f name empty-shift-cache)]
     [(name enclosing)
      (make-self-module-path-index (build-module-name name
                                                      (and enclosing
@@ -310,7 +313,7 @@
   (begin0
     (or (let ([e (hash-ref generic-self-mpis r #f)])
           (and e (ephemeron-value e)))
-        (let ([mpi (module-path-index #f #f r #f)])
+        (let ([mpi (module-path-index #f #f r empty-shift-cache)])
           (hash-set! generic-self-mpis r (make-ephemeron r mpi))
           mpi))
     (end-atomic)))
@@ -346,28 +349,35 @@
        [(shift-cache-ref (module-path-index-shift-cache shifted-base) mpi)]
        [else
         (define shifted-mpi
-          (module-path-index (module-path-index-path mpi) shifted-base #f #f))
-        (shift-cache-set! (module-path-index-shift-cache! shifted-base) mpi shifted-mpi)
+          (module-path-index (module-path-index-path mpi) shifted-base #f empty-shift-cache))
+        (shift-cache-set! shifted-base shifted-mpi)
         shifted-mpi])])]))
 
-(define (module-path-index-shift-cache! mpi)
-  (or (let ([cache (module-path-index-shift-cache mpi)])
-        (and cache
-             (weak-box-value cache)
-             cache))
-      (let ([cache (make-weak-box (box #hasheq()))])
-        (set-module-path-index-shift-cache! mpi cache)
-        cache)))
+(define (shift-cache-ref cache mpi)
+  (for/or ([wb (in-list cache)])
+    (define v (weak-box-value wb))
+    (and v
+         (equal? (module-path-index-path v)
+                 (module-path-index-path mpi))
+         v)))
 
-(define (shift-cache-ref cache v)
-  (and cache
-       (let ([b (weak-box-value cache)])
-         (and b (hash-ref (unbox b) v #f)))))
-
-(define (shift-cache-set! cache v r)
-  (define b (weak-box-value cache))
-  (when b
-    (set-box! b (hash-set (unbox b) v r))))
+(define (shift-cache-set! base v)
+  (define new-cache
+    (cons (make-weak-box v)
+          ;; Prune empty cache entries, and keep only up to a certain
+          ;; number of cached values to avoid quadratic behavior.
+          (let loop ([n 32] [l (module-path-index-shift-cache base)])
+            (cond
+              [(null? l) null]
+              [(eqv? n 0) null]
+              [(not (weak-box-value (car l)))
+               (loop n (cdr l))]
+              [else
+               (let ([r (loop (fx- n 1) (cdr l))])
+                 (if (eq? r (cdr l))
+                     l
+                     (cons (car l) r)))]))))
+  (set-module-path-index-shift-cache! base new-cache))
 
 ;; A constant module path index to represent the top level
 (define top-level-module-path-index
diff --git a/racket/src/racket/src/startup.inc b/racket/src/racket/src/startup.inc
index a62f475a5c..bfb8721bd6 100644
--- a/racket/src/racket/src/startup.inc
+++ b/racket/src/racket/src/startup.inc
@@ -2876,6 +2876,7 @@ static const char *startup_source =
 " extra-depth_0)"
 "(unsafe-place-local-set! cell.4$2 extra-depth_0)"
 "(unsafe-place-local-set! cell.1$10(current-thread)))))))))))))))"
+" (define-values (not-an-fX.1) (lambda (who_0 v_0) (begin 'not-an-fX (raise-argument-error who_0 \"fixnum?\" v_0))))"
 "(define-values(prop:serialize serialize? serialize-ref)(make-struct-type-property 'serialize))"
 "(define-values"
 "(prop:serialize-fill! serialize-fill!? serialize-fill!-ref)"
@@ -4586,6 +4587,7 @@ static const char *startup_source =
 "(make-struct-field-accessor -ref_0 3 'shift-cache)"
 "(make-struct-field-mutator -set!_0 2 'resolved)"
 "(make-struct-field-mutator -set!_0 3 'shift-cache))))"
+"(define-values(empty-shift-cache) '())"
 "(define-values"
 "(deserialize-module-path-index)"
 "(case-lambda"
@@ -4738,7 +4740,7 @@ static const char *startup_source =
 "(let-values() base_0)))))))))"
 " loop_0)"
 " mod-path_0)))"
-"(module-path-index2.1 mod-path_0 keep-base_0 #f #f)))))))))))))))"
+"(module-path-index2.1 mod-path_0 keep-base_0 #f empty-shift-cache)))))))))))))))"
 "(case-lambda"
 "((mod-path_0 base_0)(begin 'module-path-index-join(module-path-index-join_0 mod-path_0 base_0 #f)))"
 "((mod-path_0 base_0 submod5_0)(module-path-index-join_0 mod-path_0 base_0 submod5_0)))))"
@@ -4776,7 +4778,7 @@ static const char *startup_source =
 "(define-values"
 "(make-self-module-path-index)"
 "(case-lambda"
-"((name_0)(begin(module-path-index2.1 #f #f name_0 #f)))"
+"((name_0)(begin(module-path-index2.1 #f #f name_0 empty-shift-cache)))"
 "((name_0 enclosing_0)"
 "(make-self-module-path-index"
 "(let-values(((name19_0) name_0)((temp20_0)(if enclosing_0(1/module-path-index-resolve enclosing_0) #f)))"
@@ -4797,7 +4799,7 @@ static const char *startup_source =
 "(if e_0(ephemeron-value e_0) #f))))"
 "(if or-part_0"
 " or-part_0"
-"(let-values(((mpi_0)(module-path-index2.1 #f #f r_0 #f)))"
+"(let-values(((mpi_0)(module-path-index2.1 #f #f r_0 empty-shift-cache)))"
 "(begin(hash-set!(unsafe-place-local-ref cell.1$8) r_0(make-ephemeron r_0 mpi_0)) mpi_0))))"
 "(end-atomic)))))))"
 "(define-values"
@@ -4835,31 +4837,70 @@ static const char *startup_source =
 " c1_0"
 "(let-values()"
 "(let-values(((shifted-mpi_0)"
-"(module-path-index2.1(module-path-index-path mpi_0) shifted-base_0 #f #f)))"
-"(begin"
-"(shift-cache-set!(module-path-index-shift-cache! shifted-base_0) mpi_0 shifted-mpi_0)"
-" shifted-mpi_0)))))))))))))))"
-"(define-values"
-"(module-path-index-shift-cache!)"
-"(lambda(mpi_0)"
-"(begin"
-"(let-values(((or-part_0)"
-"(let-values(((cache_0)(module-path-index-shift-cache mpi_0)))"
-"(if cache_0(if(weak-box-value cache_0) cache_0 #f) #f))))"
-"(if or-part_0"
-" or-part_0"
-"(let-values(((cache_0)(make-weak-box(box '#hasheq()))))"
-"(begin(set-module-path-index-shift-cache! mpi_0 cache_0) cache_0)))))))"
+"(module-path-index2.1"
+"(module-path-index-path mpi_0)"
+" shifted-base_0"
+" #f"
+" empty-shift-cache)))"
+"(begin(shift-cache-set! shifted-base_0 shifted-mpi_0) shifted-mpi_0)))))))))))))))"
 "(define-values"
 "(shift-cache-ref)"
-"(lambda(cache_0 v_0)"
-"(begin(if cache_0(let-values(((b_0)(weak-box-value cache_0)))(if b_0(hash-ref(unbox b_0) v_0 #f) #f)) #f))))"
+"(lambda(cache_0 mpi_0)"
+"(begin"
+"(let-values(((lst_0) cache_0))"
+"(begin"
+"(if(variable-reference-from-unsafe?(#%variable-reference))(void)(let-values()(check-list lst_0)))"
+"((letrec-values(((for-loop_0)"
+"(lambda(result_0 lst_1)"
+"(begin"
+" 'for-loop"
+"(if(pair? lst_1)"
+"(let-values(((wb_0)(unsafe-car lst_1))((rest_0)(unsafe-cdr lst_1)))"
+"(let-values(((result_1)"
+"(let-values()"
+"(let-values(((result_1)"
+"(let-values()"
+"(let-values()"
+"(let-values(((v_0)(weak-box-value wb_0)))"
+"(if v_0"
+"(if(equal?"
+"(module-path-index-path v_0)"
+"(module-path-index-path mpi_0))"
+" v_0"
+" #f)"
+" #f))))))"
+"(values result_1)))))"
+"(if(if(not((lambda x_0 result_1) wb_0))(not #f) #f)"
+"(for-loop_0 result_1 rest_0)"
+" result_1)))"
+" result_0)))))"
+" for-loop_0)"
+" #f"
+" lst_0))))))"
 "(define-values"
 "(shift-cache-set!)"
-"(lambda(cache_0 v_0 r_0)"
+"(lambda(base_0 v_0)"
 "(begin"
-"(let-values(((b_0)(weak-box-value cache_0)))"
-"(if b_0(let-values()(set-box! b_0(hash-set(unbox b_0) v_0 r_0)))(void))))))"
+"(let-values(((new-cache_0)"
+"(cons"
+"(make-weak-box v_0)"
+"((letrec-values(((loop_0)"
+"(lambda(n_0 l_0)"
+"(begin"
+" 'loop"
+"(if(null? l_0)"
+"(let-values() null)"
+"(if(eqv? n_0 0)"
+"(let-values() null)"
+"(if(not(weak-box-value(car l_0)))"
+"(let-values()(loop_0 n_0(cdr l_0)))"
+"(let-values()"
+"(let-values(((r_0)(loop_0(fx- n_0 1)(cdr l_0))))"
+"(if(eq? r_0(cdr l_0)) l_0(cons(car l_0) r_0)))))))))))"
+" loop_0)"
+" 32"
+"(module-path-index-shift-cache base_0)))))"
+"(set-module-path-index-shift-cache! base_0 new-cache_0)))))"
 "(define-values(top-level-module-path-index)(make-self-module-path-index(1/make-resolved-module-path 'top-level)))"
 "(define-values(top-level-module-path-index?)(lambda(mpi_0)(begin(eq? top-level-module-path-index mpi_0))))"
 "(define-values(non-self-module-path-index?)(lambda(mpi_0)(begin(if(module-path-index-path mpi_0) #t #f))))"
@@ -5278,7 +5319,6 @@ static const char *startup_source =
 "(pop-syntax-context!)"
 "(lambda(state_0)"
 "(begin(let-values(((b_0)(serialize-state-syntax-context state_0)))(set-box! b_0(cdr(unbox b_0)))))))"
-" (define-values (not-an-fX.1) (lambda (who_0 v_0) (begin 'not-an-fX (raise-argument-error who_0 \"fixnum?\" v_0))))"
 "(define-values(root-tag)(unsafe-root-continuation-prompt-tag))"
 "(define-values(default-val.1$2) #f)"
 "(define-values"