diff --git a/components/js/prophet-wasmstan/package-lock.json b/components/js/prophet-wasmstan/package-lock.json
index b246f02b..f530d3f0 100644
--- a/components/js/prophet-wasmstan/package-lock.json
+++ b/components/js/prophet-wasmstan/package-lock.json
@@ -9,16 +9,16 @@
       "version": "0.2.0",
       "license": "(MIT OR Apache-2.0)",
       "dependencies": {
-        "@bytecodealliance/preview2-shim": "^0.17.3"
+        "@bytecodealliance/preview2-shim": "^0.21.0"
       },
       "devDependencies": {
         "vitest": "4.1.10"
       }
     },
     "node_modules/@bytecodealliance/preview2-shim": {
-      "version": "0.17.9",
-      "resolved": "https://registry.npmjs.org/@bytecodealliance/preview2-shim/-/preview2-shim-0.17.9.tgz",
-      "integrity": "sha512-i0R3eQBe6PA/o/1EFE3Owe4In2rcccb6QxnjpntM/lPe3/duJ0bRQTVZM2Ufpo99X4eofGeltQUkape1C91FFA==",
+      "version": "0.21.0",
+      "resolved": "https://registry.npmjs.org/@bytecodealliance/preview2-shim/-/preview2-shim-0.21.0.tgz",
+      "integrity": "sha512-rl1NnsvBlL6Q912BUkYotiZ6L/LE8SJUnvJOuElp/kjULHnAaz8Zn4qeBiiiRmQcoZGYXXrW5dhEbPeYtcxXXQ==",
       "license": "(Apache-2.0 WITH LLVM-exception)"
     },
     "node_modules/@emnapi/core": {
diff --git a/components/js/prophet-wasmstan/package.json b/components/js/prophet-wasmstan/package.json
index 793bd56e..8a09b8eb 100644
--- a/components/js/prophet-wasmstan/package.json
+++ b/components/js/prophet-wasmstan/package.json
@@ -28,7 +28,7 @@
     "stan"
   ],
   "dependencies": {
-    "@bytecodealliance/preview2-shim": "^0.17.3"
+    "@bytecodealliance/preview2-shim": "^0.21.0"
   },
   "devDependencies": {
     "vitest": "4.1.10"
diff --git a/demo/dist/@bsull/augurs-prophet-wasmstan/package.json b/demo/dist/@bsull/augurs-prophet-wasmstan/package.json
index f4bad08c..8a09b8eb 100644
--- a/demo/dist/@bsull/augurs-prophet-wasmstan/package.json
+++ b/demo/dist/@bsull/augurs-prophet-wasmstan/package.json
@@ -28,7 +28,7 @@
     "stan"
   ],
   "dependencies": {
-    "@bytecodealliance/preview2-shim": "^0.17.0"
+    "@bytecodealliance/preview2-shim": "^0.21.0"
   },
   "devDependencies": {
     "vitest": "4.1.10"