diff --git a/packages/proto-signing/src/adr27.spec.ts b/packages/proto-signing/src/adr27.spec.ts
index 7d185e86..257bc9ad 100644
--- a/packages/proto-signing/src/adr27.spec.ts
+++ b/packages/proto-signing/src/adr27.spec.ts
@@ -1,4 +1,5 @@
 import { fromHex } from "@cosmjs/encoding";
+import Long from "long";
 import { parse } from "protobufjs";
 
 import { omitDefault, omitDefaults } from "./adr27";
@@ -25,6 +26,16 @@ describe("adr27", () => {
       expect(omitDefault(0.0)).toEqual(null);
     });
 
+    it("works for Long", () => {
+      // unsigned
+      expect(omitDefault(Long.fromNumber(123, true))).toEqual(Long.fromNumber(123, true));
+      expect(omitDefault(Long.fromNumber(0, true))).toEqual(null);
+
+      // signed
+      expect(omitDefault(Long.fromNumber(123, false))).toEqual(Long.fromNumber(123, false));
+      expect(omitDefault(Long.fromNumber(0, false))).toEqual(null);
+    });
+
     it("works for booleans", () => {
       expect(omitDefault(true)).toEqual(true);
       expect(omitDefault(false)).toEqual(null);
@@ -73,6 +84,12 @@ describe("adr27", () => {
       expect(omitDefaults(1.234)).toEqual(1.234);
       expect(omitDefaults(0.0)).toEqual(null);
 
+      expect(omitDefaults(Long.fromNumber(123, true))).toEqual(Long.fromNumber(123, true));
+      expect(omitDefaults(Long.fromNumber(0, true))).toEqual(null);
+
+      expect(omitDefaults(Long.fromNumber(123, false))).toEqual(Long.fromNumber(123, false));
+      expect(omitDefaults(Long.fromNumber(0, false))).toEqual(null);
+
       expect(omitDefaults(true)).toEqual(true);
       expect(omitDefaults(false)).toEqual(null);
     });
diff --git a/packages/proto-signing/src/adr27.ts b/packages/proto-signing/src/adr27.ts
index 870c953e..77a9f506 100644
--- a/packages/proto-signing/src/adr27.ts
+++ b/packages/proto-signing/src/adr27.ts
@@ -1,4 +1,5 @@
 import { isNonNullObject, isUint8Array } from "@cosmjs/utils";
+import Long from "long";
 
 /**
  * Converts default values to null in order to tell protobuf.js
@@ -13,6 +14,10 @@ export function omitDefault<T>(input: T): T | null {
     return input || null;
   }
 
+  if (Long.isLong(input)) {
+    return !input.isZero() ? input : null;
+  }
+
   if (Array.isArray(input) || isUint8Array(input)) {
     return input.length ? input : null;
   }
@@ -33,6 +38,7 @@ export function omitDefaults(input: any): any {
     typeof input === "number" ||
     typeof input === "boolean" ||
     typeof input === "string" ||
+    Long.isLong(input) ||
     Array.isArray(input) ||
     isUint8Array(input)
   ) {