diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87fcd394..b2bdfe2a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@
   remove such functionality from `CosmosClient.searchTx`.
 - @cosmjs/launchpad: Add `SigningCosmosClient.sign` method for signing without
   broadcasting.
+- @cosmjs/launchpad: Add support for undefined memo in `makeSignDoc`.
 - @cosmjs/launchpad-ledger: `LedgerSigner.sign` method renamed `signAmino`.
 - @cosmjs/proto-signing: Add new package for handling transaction signing with
   protobuf encoding.
diff --git a/packages/launchpad/src/encoding.spec.ts b/packages/launchpad/src/encoding.spec.ts
index 1ac93c9c..45fd1727 100644
--- a/packages/launchpad/src/encoding.spec.ts
+++ b/packages/launchpad/src/encoding.spec.ts
@@ -1,4 +1,8 @@
-import { sortedJsonStringify } from "./encoding";
+/* eslint-disable @typescript-eslint/naming-convention */
+import { coin, coins } from "./coins";
+import { makeSignDoc, sortedJsonStringify } from "./encoding";
+import { MsgDelegate, MsgSend } from "./msgs";
+import { faucet, launchpad, makeRandomAddress } from "./testutils.spec";
 
 describe("encoding", () => {
   describe("sortedJsonStringify", () => {
@@ -47,4 +51,79 @@ describe("encoding", () => {
       );
     });
   });
+
+  describe("makeSignDoc", () => {
+    it("works", () => {
+      const chainId = "testspace-12";
+      const msg1: MsgDelegate = {
+        type: "cosmos-sdk/MsgDelegate",
+        value: {
+          delegator_address: faucet.address,
+          validator_address: launchpad.validator.address,
+          amount: coin(1234, "ustake"),
+        },
+      };
+      const msg2: MsgSend = {
+        type: "cosmos-sdk/MsgSend",
+        value: {
+          from_address: faucet.address,
+          to_address: makeRandomAddress(),
+          amount: coins(1234567, "ucosm"),
+        },
+      };
+      const fee = {
+        amount: coins(2000, "ucosm"),
+        gas: "180000", // 180k
+      };
+      const memo = "Use your power wisely";
+      const accountNumber = 15;
+      const sequence = 16;
+
+      const signDoc = makeSignDoc([msg1, msg2], fee, chainId, memo, accountNumber, sequence);
+      expect(signDoc).toEqual({
+        msgs: [msg1, msg2],
+        fee: fee,
+        chain_id: chainId,
+        account_number: accountNumber.toString(),
+        sequence: sequence.toString(),
+        memo: memo,
+      });
+    });
+
+    it("works with undefined memo", () => {
+      const chainId = "testspace-12";
+      const msg1: MsgDelegate = {
+        type: "cosmos-sdk/MsgDelegate",
+        value: {
+          delegator_address: faucet.address,
+          validator_address: launchpad.validator.address,
+          amount: coin(1234, "ustake"),
+        },
+      };
+      const msg2: MsgSend = {
+        type: "cosmos-sdk/MsgSend",
+        value: {
+          from_address: faucet.address,
+          to_address: makeRandomAddress(),
+          amount: coins(1234567, "ucosm"),
+        },
+      };
+      const fee = {
+        amount: coins(2000, "ucosm"),
+        gas: "180000", // 180k
+      };
+      const accountNumber = 15;
+      const sequence = 16;
+
+      const signDoc = makeSignDoc([msg1, msg2], fee, chainId, undefined, accountNumber, sequence);
+      expect(signDoc).toEqual({
+        msgs: [msg1, msg2],
+        fee: fee,
+        chain_id: chainId,
+        account_number: accountNumber.toString(),
+        sequence: sequence.toString(),
+        memo: "",
+      });
+    });
+  });
 });
diff --git a/packages/launchpad/src/encoding.ts b/packages/launchpad/src/encoding.ts
index 6090cc79..27d058b7 100644
--- a/packages/launchpad/src/encoding.ts
+++ b/packages/launchpad/src/encoding.ts
@@ -47,7 +47,7 @@ export function makeSignDoc(
   msgs: readonly Msg[],
   fee: StdFee,
   chainId: string,
-  memo: string,
+  memo: string | undefined,
   accountNumber: number | string,
   sequence: number | string,
 ): StdSignDoc {
@@ -57,7 +57,7 @@ export function makeSignDoc(
     sequence: Uint53.fromString(sequence.toString()).toString(),
     fee: fee,
     msgs: msgs,
-    memo: memo,
+    memo: memo || "",
   };
 }
 
diff --git a/packages/launchpad/types/encoding.d.ts b/packages/launchpad/types/encoding.d.ts
index 0cad6f04..cb20550d 100644
--- a/packages/launchpad/types/encoding.d.ts
+++ b/packages/launchpad/types/encoding.d.ts
@@ -19,7 +19,7 @@ export declare function makeSignDoc(
   msgs: readonly Msg[],
   fee: StdFee,
   chainId: string,
-  memo: string,
+  memo: string | undefined,
   accountNumber: number | string,
   sequence: number | string,
 ): StdSignDoc;