diff --git a/README.md b/README.md
index ab3470f..9652e0a 100644
--- a/README.md
+++ b/README.md
@@ -21,12 +21,24 @@ The focus of VeRT is on the better compatibility than the performance, so it can
 ## Chain compatibility
 
 Antelope chains do not all expose the same host functions, and a harness that offers more than the
-target chain will link a contract that the chain rejects at `setcode`.
+target chain will link a contract that the chain rejects at `setcode`. To keep a passing suite
+meaningful, chain-specific host functions are withheld unless the emulated chain provides them.
 
-`verify_rsa_sha256_sig` is currently registered for every `Blockchain`. It exists on WAX; it does not
-exist on EOS, Jungle4, or Vaulta. A contract that calls it therefore passes here and fails to load on
-those chains. Until the host function set is selectable per chain, treat a passing suite as evidence
-for WAX only when RSA is involved.
+A `Blockchain` emulates generic Antelope by default, which exposes no chain-specific host functions.
+Name a chain to add the ones unique to it:
+
+```typescript
+const bc = new Blockchain();                  // generic Antelope
+const wax = new Blockchain({ chain: 'wax' });  // adds verify_rsa_sha256_sig
+```
+
+`verify_rsa_sha256_sig` exists on WAX and not on EOS, Jungle4, or Vaulta. A contract that imports it
+instantiates under a `wax` blockchain and fails to instantiate under any other, which mirrors how
+`setcode` accepts it on WAX and rejects it elsewhere. Test WAX contracts that use RSA against a
+`wax` blockchain, and test everything else against the default.
+
+The chain-specific host functions are declared in `CHAIN_SPECIFIC_HOST_FUNCTIONS`; add an entry
+there to model a new one.
 
 ## Installation
 
diff --git a/examples/rsa/rsa.spec.ts b/examples/rsa/rsa.spec.ts
index f3d89da..f90d888 100644
--- a/examples/rsa/rsa.spec.ts
+++ b/examples/rsa/rsa.spec.ts
@@ -30,7 +30,7 @@ const modulus1 =
   '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';
 
 // Initialize blockchain
-const blockchain = new Blockchain();
+const blockchain = new Blockchain({ chain: 'wax' }); // verify_rsa_sha256_sig is a WAX host function
 
 // Create RSA contract
 const contractName = Name.from('rsa');
diff --git a/package.json b/package.json
index 65e805a..3f6713c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@atomichub/vert",
-  "version": "2.1.1",
+  "version": "2.2.0",
   "homepage": "https://github.com/atomicassets/vert",
   "description": "Testing library for Antelope smart contracts, with per-chain host function parity",
   "main": "dist/index.js",
diff --git a/src/antelope/blockchain.ts b/src/antelope/blockchain.ts
index 1b5094f..ebd02d0 100644
--- a/src/antelope/blockchain.ts
+++ b/src/antelope/blockchain.ts
@@ -14,6 +14,20 @@ import colors from 'colors'
 import { ACTIVATED_PROTOCOL_FEATURES } from "../utils/activatedFeatures";
 import Buffer from '../buffer'
 
+// Host functions that only some Antelope chains expose. A contract importing one
+// fails to load (setcode) on a chain that lacks it, so the VM must withhold it
+// on those chains too, or a passing test would not reflect the target chain.
+// Keyed by chain, valued by the host functions unique to it.
+export const CHAIN_SPECIFIC_HOST_FUNCTIONS: Record<string, readonly string[]> = {
+  wax: ['verify_rsa_sha256_sig'],
+}
+
+// The union of every chain-specific host function, used by the VM to withhold
+// any that the target chain does not provide.
+export const ALL_CHAIN_SPECIFIC_HOST_FUNCTIONS: ReadonlySet<string> = new Set(
+  Object.values(CHAIN_SPECIFIC_HOST_FUNCTIONS).flat()
+)
+
 export class Blockchain {
   accounts: { [key: string]: Account }
   timestamp: TimePoint
@@ -30,22 +44,36 @@ export class Blockchain {
   postStorage: any
   storageDeltaChangesets: any
   _storageDeltas: any
-  
+
+  // The chain being emulated, if any. Undefined means generic Antelope, which
+  // exposes no chain-specific host functions. Naming a chain (e.g. 'wax') adds
+  // the host functions unique to it.
+  chain?: string
+
   constructor ({
     accounts,
     timestamp,
     blockNum,
     store,
+    chain,
   }: {
     accounts?: { [key: string]: Account },
     timestamp?: TimePoint,
     blockNum?: number,
-    store?: TableStore
+    store?: TableStore,
+    chain?: string
   } = {}) {
     this.accounts = accounts || {}
     this.timestamp = timestamp || TimePoint.fromMilliseconds(0)
     this.blockNum = blockNum || 0
     this.store = store || new TableStore()
+    this.chain = chain
+  }
+
+  // The chain-specific host functions this chain provides. Generic Antelope
+  // provides none.
+  enabledChainHostFunctions (): ReadonlySet<string> {
+    return new Set(this.chain ? (CHAIN_SPECIFIC_HOST_FUNCTIONS[this.chain] ?? []) : [])
   }
 
   private applyTransactionActions(transaction: Transaction, decodedData?: any) {
diff --git a/src/antelope/tests/vm.spec.ts b/src/antelope/tests/vm.spec.ts
index 979fea8..ae55027 100644
--- a/src/antelope/tests/vm.spec.ts
+++ b/src/antelope/tests/vm.spec.ts
@@ -10,16 +10,23 @@ const NodeRSA = require('node-rsa');
 const crypto = require('crypto');
 
 const bc = new Blockchain()
+// A WAX chain exposes verify_rsa_sha256_sig, which generic Antelope withholds.
+const waxBc = new Blockchain({ chain: 'wax' })
 
 let vm;
+let waxVm;
 let memory;
 
 beforeEach(() => {
   bc.clearConsole()
-  vm = VM.from(new Uint8Array(), bc);
+  waxBc.clearConsole()
   memory = Memory.create(256);
+  vm = VM.from(new Uint8Array(), bc);
+  waxVm = VM.from(new Uint8Array(), waxBc);
   // @ts-ignore
   vm._memory = memory;
+  // @ts-ignore
+  waxVm._memory = memory;
 });
 
 describe('eos-vm imports', () => {
@@ -108,7 +115,7 @@ describe('eos-vm imports', () => {
       const modulusLen = modulus.length;
 
       // Call assert_valid_rsa_sig - should not throw
-      let valid = vm.imports.env.verify_rsa_sha256_sig(
+      let valid = waxVm.imports.env.verify_rsa_sha256_sig(
         messageHashOffset, messageHashLen,
         signatureOffset, signatureLen,
         exponentOffset, exponentLen,
@@ -169,7 +176,7 @@ describe('eos-vm imports', () => {
       const modulusLen = modulus.length;
 
       // Call assert_invalid_rsa_sig - should not throw because signature is indeed invalid
-      let result = vm.imports.env.verify_rsa_sha256_sig(
+      let result = waxVm.imports.env.verify_rsa_sha256_sig(
         messageHashOffset, messageHashLen,
         signatureOffset, signatureLen,
         exponentOffset, exponentLen,
@@ -201,6 +208,29 @@ describe('eos-vm imports', () => {
     });
   });
 
+  describe('chain-specific host functions', () => {
+    it('generic Antelope withholds verify_rsa_sha256_sig', () => {
+      // A contract importing it would fail to instantiate here, exactly as
+      // setcode rejects it on EOS, Jungle4 and Vaulta.
+      expect(vm.imports.env.verify_rsa_sha256_sig).to.equal(undefined);
+    });
+
+    it('a WAX chain provides verify_rsa_sha256_sig', () => {
+      expect(waxVm.imports.env.verify_rsa_sha256_sig).to.be.a('function');
+    });
+
+    it('an unknown chain name withholds it', () => {
+      const other = VM.from(new Uint8Array(), new Blockchain({ chain: 'not-a-chain' }));
+      expect(other.imports.env.verify_rsa_sha256_sig).to.equal(undefined);
+    });
+
+    it('withholding a chain-specific function does not disturb the shared ones', () => {
+      // recover_key exists on every chain, so it must survive the gate on both.
+      expect(vm.imports.env.recover_key).to.be.a('function');
+      expect(waxVm.imports.env.recover_key).to.be.a('function');
+    });
+  });
+
   describe('print', () => {
     it('prints', () => {
       const buffer = Buffer.from_(memory.buffer);
diff --git a/src/antelope/vm.ts b/src/antelope/vm.ts
index 3b94217..01f53dc 100644
--- a/src/antelope/vm.ts
+++ b/src/antelope/vm.ts
@@ -7,7 +7,7 @@ import { Action, Name, NameType, PermissionLevel, PublicKey, Serializer, Signatu
 import { sha256, sha512, sha1, ripemd160 } from "hash.js";
 import { sha3_256, keccak256 } from "js-sha3"
 import { bigIntToName, nameToBigInt, nameTypeToBigInt } from "./bn";
-import { Blockchain } from "./blockchain";
+import { Blockchain, ALL_CHAIN_SPECIFIC_HOST_FUNCTIONS } from "./blockchain";
 import { Account } from "./account";
 import { antelopeAssert, antelopeAssertMessage, antelopeAssertCode } from "./errors";
 import { isAuthoritySatisfied } from "./utils";
@@ -1474,6 +1474,16 @@ class VM extends Vert {
       },
     };
 
+    // Withhold chain-specific host functions the target chain does not provide,
+    // so a contract importing one fails to instantiate here exactly as setcode
+    // would reject it on that chain. Generic Antelope withholds all of them.
+    const enabledChainHostFunctions = bc.enabledChainHostFunctions();
+    for (const fn of ALL_CHAIN_SPECIFIC_HOST_FUNCTIONS) {
+      if (!enabledChainHostFunctions.has(fn)) {
+        delete (imports.env as any)[fn];
+      }
+    }
+
     super(imports, wasm);
     this.imports = imports;
     this.bc = bc;