diff --git a/native-pkgs b/native-pkgs
index 8988164a6e..a4521921ce 160000
--- a/native-pkgs
+++ b/native-pkgs
@@ -1 +1 @@
-Subproject commit 8988164a6e18abb1b796add19a6941021f61db56
+Subproject commit a4521921cea66170c4b55373cda6191fb47730d5
diff --git a/racket/src/native-libs/build.rkt b/racket/src/native-libs/build.rkt
index 20b1d590b8..7a29aef1ac 100644
--- a/racket/src/native-libs/build.rkt
+++ b/racket/src/native-libs/build.rkt
@@ -296,7 +296,10 @@
                                         (if win?
                                             '("libiconv")
                                             '()))
-                      #:env path-flags
+                      #:env (append path-flags
+                                    ;; Disable Valgrind support, which particularly
+                                    ;; goes wrong for 64-bit Windows builds.
+                                    (list (list "CPPFLAGS" "-DNVALGRIND=1")))
                       #:patches (if (and win? m32?)
                                     (list rand-patch)
                                     null))]