diff --git a/.changeset/canonical-mnemonic-phrase.md b/.changeset/canonical-mnemonic-phrase.md
new file mode 100644
index 0000000..ed8e184
--- /dev/null
+++ b/.changeset/canonical-mnemonic-phrase.md
@@ -0,0 +1,5 @@
+---
+"@swapkit/wallets": patch
+---
+
+The keystore wallet now cleans up a seed phrase before deriving any key, using `canonicalizeMnemonic` from `@swapkit/helpers`. A phrase pasted with tabs, repeated spaces, non-breaking spaces or a trailing newline connects to the same addresses as the clean phrase, a phrase with a bad checksum is rejected with `wallet_keystore_invalid_phrase`, and `validatePhrase` follows the same rules. Clean phrases are unaffected.
diff --git a/packages/wallets/src/keystore-helpers.ts b/packages/wallets/src/keystore-helpers.ts
index 1bde34b..1d8eea8 100644
--- a/packages/wallets/src/keystore-helpers.ts
+++ b/packages/wallets/src/keystore-helpers.ts
@@ -1,7 +1,7 @@
 import { createCipheriv, createDecipheriv, pbkdf2Sync, randomBytes } from "node:crypto";
-import { generateMnemonic, validateMnemonic } from "@scure/bip39";
+import { generateMnemonic } from "@scure/bip39";
 import { wordlist } from "@scure/bip39/wordlists/english.js";
-import { SwapKitError } from "@swapkit/helpers";
+import { canonicalizeMnemonic, SwapKitError } from "@swapkit/helpers";
 
 export type PhraseWordCount = 12 | 15 | 18 | 21 | 24;
 
@@ -77,7 +77,12 @@ export async function generateKeystore({
 }
 
 export function validatePhrase(phrase: string) {
-  return validateMnemonic(phrase, wordlist);
+  try {
+    canonicalizeMnemonic(phrase);
+    return true;
+  } catch {
+    return false;
+  }
 }
 
 export async function decryptFromKeystore(keystore: Keystore, password: string) {
diff --git a/packages/wallets/src/keystore.ts b/packages/wallets/src/keystore.ts
index 39a6157..287359f 100644
--- a/packages/wallets/src/keystore.ts
+++ b/packages/wallets/src/keystore.ts
@@ -3,6 +3,7 @@ import {
   type AssetValue,
   Chain,
   CosmosChains,
+  canonicalizeMnemonic,
   type DerivationPathArray,
   EVMChains,
   filterSupportedChains,
@@ -209,6 +210,7 @@ export async function createKeystoreWallet<T extends Chain[]>({
     supportedChains: KEYSTORE_SUPPORTED_CHAINS,
     walletType: WalletOption.KEYSTORE,
   });
+  const canonicalPhrase = canonicalizeMnemonic(phrase);
 
   const walletIndex = typeof derivationPathMapOrIndex === "number" ? derivationPathMapOrIndex : 0;
   const walletResults = await Promise.allSettled(
@@ -241,7 +243,7 @@ export async function createKeystoreWallet<T extends Chain[]>({
 
       const toolbox = await getToolbox(chain, {
         derivationPath,
-        phrase,
+        phrase: canonicalPhrase,
         ...(resolvedScriptType ? { scriptType: resolvedScriptType } : {}),
       });
       const address = (await toolbox.getAddress()) || "";
diff --git a/packages/wallets/test/keystore.test.ts b/packages/wallets/test/keystore.test.ts
index 14cafa0..245df89 100644
--- a/packages/wallets/test/keystore.test.ts
+++ b/packages/wallets/test/keystore.test.ts
@@ -93,3 +93,28 @@ describe("keystore phrase generation", () => {
     expect(await decryptFromKeystore(keystore, "password")).toBe(phrase);
   });
 });
+
+describe("keystore phrase canonicalisation", () => {
+  test("a phrase with stray whitespace connects to the same addresses as the clean phrase", async () => {
+    const messy = `\n${TEST_PHRASE.split(" ").join("\t  ")}\u00a0\r\n`;
+    const chains = [Chain.Bitcoin, Chain.Ethereum, Chain.Solana];
+
+    const clean = await createKeystoreWallet({ chains, phrase: TEST_PHRASE });
+    const dirty = await createKeystoreWallet({ chains, phrase: messy });
+
+    for (const chain of chains) {
+      expect(clean[chain]?.address).toBeTruthy();
+      expect(`${chain}: ${dirty[chain]?.address}`).toBe(`${chain}: ${clean[chain]?.address}`);
+    }
+    expect(validatePhrase(messy)).toBe(true);
+  });
+
+  test("a phrase with a bad checksum is rejected before any chain connects", async () => {
+    const badChecksum = TEST_PHRASE.replace("about", "abandon");
+
+    expect(validatePhrase(badChecksum)).toBe(false);
+    await expect(createKeystoreWallet({ chains: [Chain.Ethereum], phrase: badChecksum })).rejects.toThrow(
+      "wallet_keystore_invalid_phrase",
+    );
+  });
+});