diff --git a/packages/stargate/src/stargateclient.ts b/packages/stargate/src/stargateclient.ts
index 4b96bf19..ec23473c 100644
--- a/packages/stargate/src/stargateclient.ts
+++ b/packages/stargate/src/stargateclient.ts
@@ -3,7 +3,7 @@ import { Bech32, toAscii, toHex } from "@cosmjs/encoding";
 import { Uint64 } from "@cosmjs/math";
 import { BaseAccount, Coin, decodeAny } from "@cosmjs/proto-signing";
 import { Client as TendermintClient } from "@cosmjs/tendermint-rpc";
-import { assert } from "@cosmjs/utils";
+import { assertDefined } from "@cosmjs/utils";
 import Long from "long";
 
 export interface GetSequenceResult {
@@ -37,8 +37,8 @@ export class StargateClient {
     switch (typeUrl) {
       case "/cosmos.auth.BaseAccount": {
         const { account_number, sequence } = BaseAccount.decode(value);
-        assert(account_number !== undefined);
-        assert(sequence !== undefined);
+        assertDefined(account_number);
+        assertDefined(sequence);
         return {
           accountNumber: uint64FromProto(account_number).toNumber(),
           sequence: uint64FromProto(sequence).toNumber(),
@@ -67,8 +67,8 @@ export class StargateClient {
 
     const responseData = await this.queryVerified("bank", bankKey);
     const { amount, denom } = Coin.decode(responseData);
-    assert(amount !== undefined);
-    assert(denom !== undefined);
+    assertDefined(amount);
+    assertDefined(denom);
 
     if (denom === "") {
       return null;
diff --git a/packages/utils/src/assert.spec.ts b/packages/utils/src/assert.spec.ts
new file mode 100644
index 00000000..4b6374cf
--- /dev/null
+++ b/packages/utils/src/assert.spec.ts
@@ -0,0 +1,52 @@
+import { assertDefined } from "./assert";
+
+describe("assert", () => {
+  describe("assertDefined", () => {
+    it("passes for simple values", () => {
+      {
+        const value: number | undefined = 123;
+        assertDefined(value);
+        expect(value).toEqual(123);
+      }
+      {
+        const value: string | undefined = "abc";
+        assertDefined(value);
+        expect(value).toEqual("abc");
+      }
+    });
+
+    it("passes for falsy values", () => {
+      {
+        const value: number | undefined = 0;
+        assertDefined(value);
+        expect(value).toEqual(0);
+      }
+      {
+        const value: string | undefined = "";
+        assertDefined(value);
+        expect(value).toEqual("");
+      }
+      {
+        const value: null | undefined = null;
+        assertDefined(value);
+        expect(value).toEqual(null);
+      }
+    });
+
+    it("throws for undefined values", () => {
+      {
+        const value: number | undefined = undefined;
+        expect(() => assertDefined(value)).toThrowError("value is undefined");
+      }
+      {
+        let value: string | undefined;
+        expect(() => assertDefined(value)).toThrowError("value is undefined");
+      }
+    });
+
+    it("throws with custom message", () => {
+      const value: number | undefined = undefined;
+      expect(() => assertDefined(value, "Bug in the data source")).toThrowError("Bug in the data source");
+    });
+  });
+});
diff --git a/packages/utils/src/assert.ts b/packages/utils/src/assert.ts
index 1c35d1c0..3c86b353 100644
--- a/packages/utils/src/assert.ts
+++ b/packages/utils/src/assert.ts
@@ -4,3 +4,9 @@ export function assert(condition: any, msg?: string): asserts condition {
     throw new Error(msg || "condition is not truthy");
   }
 }
+
+export function assertDefined<T>(value: T | undefined, msg?: string): asserts value is T {
+  if (value === undefined) {
+    throw new Error(msg || "value is undefined");
+  }
+}
diff --git a/packages/utils/src/index.ts b/packages/utils/src/index.ts
index ea096301..8d7c29d4 100644
--- a/packages/utils/src/index.ts
+++ b/packages/utils/src/index.ts
@@ -1,3 +1,3 @@
-export { assert } from "./assert";
+export { assert, assertDefined } from "./assert";
 export { sleep } from "./sleep";
 export { isNonNullObject, isUint8Array } from "./typechecks";
diff --git a/packages/utils/types/assert.d.ts b/packages/utils/types/assert.d.ts
index 2e9da4bf..385fadf1 100644
--- a/packages/utils/types/assert.d.ts
+++ b/packages/utils/types/assert.d.ts
@@ -1 +1,2 @@
 export declare function assert(condition: any, msg?: string): asserts condition;
+export declare function assertDefined<T>(value: T | undefined, msg?: string): asserts value is T;
diff --git a/packages/utils/types/index.d.ts b/packages/utils/types/index.d.ts
index ea096301..8d7c29d4 100644
--- a/packages/utils/types/index.d.ts
+++ b/packages/utils/types/index.d.ts
@@ -1,3 +1,3 @@
-export { assert } from "./assert";
+export { assert, assertDefined } from "./assert";
 export { sleep } from "./sleep";
 export { isNonNullObject, isUint8Array } from "./typechecks";