diff --git a/CHANGELOG.md b/CHANGELOG.md
index 319c75d8..4dddf154 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,7 +46,10 @@ and this project adheres to
 - @cosmjs/stargate: Remove `QueryClient.queryUnverified` and
   `QueryClient.queryVerified`. Please use `QueryClient.queryAbci` and
   `QueryClient.queryStoreVerified` instead.
+- @cosmjs/stargate: Remove "not_supported_by_chain" option for Amino converter
+  types since this is not needed anymore. ([#1403])
 
+[#1403]: https://github.com/cosmos/cosmjs/issues/1403
 [#1409]: https://github.com/cosmos/cosmjs/issues/1409
 [#1411]: https://github.com/cosmos/cosmjs/pull/1411
 
diff --git a/packages/stargate/src/aminotypes.spec.ts b/packages/stargate/src/aminotypes.spec.ts
index a7d06a1b..ff768706 100644
--- a/packages/stargate/src/aminotypes.spec.ts
+++ b/packages/stargate/src/aminotypes.spec.ts
@@ -192,17 +192,6 @@ describe("AminoTypes", () => {
       });
     });
 
-    it("throws for types which are not on chain yet", () => {
-      expect(() => {
-        new AminoTypes({ "/cosmos.feegrant.v1beta1.MsgRevokeAllowance": "not_supported_by_chain" }).toAmino({
-          typeUrl: "/cosmos.feegrant.v1beta1.MsgRevokeAllowance",
-          value: 0,
-        });
-      }).toThrowError(
-        /The message type '\/cosmos.feegrant.v1beta1.MsgRevokeAllowance' cannot be signed using the Amino JSON sign mode because this is not supported by chain./i,
-      );
-    });
-
     it("throws for unknown type url", () => {
       expect(() =>
         new AminoTypes(createBankAminoConverters()).fromAmino({
diff --git a/packages/stargate/src/aminotypes.ts b/packages/stargate/src/aminotypes.ts
index cd7f83b0..f0cbdd62 100644
--- a/packages/stargate/src/aminotypes.ts
+++ b/packages/stargate/src/aminotypes.ts
@@ -9,13 +9,7 @@ export interface AminoConverter {
 }
 
 /** A map from protobuf type URL to the AminoConverter implementation if supported on chain */
-export type AminoConverters = Record<string, AminoConverter | "not_supported_by_chain">;
-
-function isAminoConverter(
-  converter: [string, AminoConverter | "not_supported_by_chain"],
-): converter is [string, AminoConverter] {
-  return typeof converter[1] !== "string";
-}
+export type AminoConverters = Record<string, AminoConverter>;
 
 /**
  * A map from Stargate message types as used in the messages's `Any` type
@@ -26,7 +20,7 @@ export class AminoTypes {
   // There is no uniqueness guarantee of the Amino type identifier in the type
   // system or constructor. Instead it's the user's responsibility to ensure
   // there is no overlap when fromAmino is called.
-  private readonly register: Record<string, AminoConverter | "not_supported_by_chain">;
+  private readonly register: Record<string, AminoConverter>;
 
   public constructor(types: AminoConverters) {
     this.register = types;
@@ -34,11 +28,6 @@ export class AminoTypes {
 
   public toAmino({ typeUrl, value }: EncodeObject): AminoMsg {
     const converter = this.register[typeUrl];
-    if (converter === "not_supported_by_chain") {
-      throw new Error(
-        `The message type '${typeUrl}' cannot be signed using the Amino JSON sign mode because this is not supported by chain.`,
-      );
-    }
     if (!converter) {
       throw new Error(
         `Type URL '${typeUrl}' does not exist in the Amino message type register. ` +
@@ -53,9 +42,7 @@ export class AminoTypes {
   }
 
   public fromAmino({ type, value }: AminoMsg): EncodeObject {
-    const matches = Object.entries(this.register)
-      .filter(isAminoConverter)
-      .filter(([_typeUrl, { aminoType }]) => aminoType === type);
+    const matches = Object.entries(this.register).filter(([_typeUrl, { aminoType }]) => aminoType === type);
 
     switch (matches.length) {
       case 0: {
diff --git a/packages/stargate/src/modules/distribution/aminomessages.ts b/packages/stargate/src/modules/distribution/aminomessages.ts
index f9844f55..12836d4e 100644
--- a/packages/stargate/src/modules/distribution/aminomessages.ts
+++ b/packages/stargate/src/modules/distribution/aminomessages.ts
@@ -72,10 +72,7 @@ export function isAminoMsgFundCommunityPool(msg: AminoMsg): msg is AminoMsgFundC
   return msg.type === "cosmos-sdk/MsgFundCommunityPool";
 }
 
-export function createDistributionAminoConverters(): Record<
-  string,
-  AminoConverter | "not_supported_by_chain"
-> {
+export function createDistributionAminoConverters(): Record<string, AminoConverter> {
   return {
     "/cosmos.distribution.v1beta1.MsgFundCommunityPool": {
       aminoType: "cosmos-sdk/MsgFundCommunityPool",
diff --git a/packages/stargate/src/modules/staking/aminomessages.ts b/packages/stargate/src/modules/staking/aminomessages.ts
index 775b0301..7b4c3732 100644
--- a/packages/stargate/src/modules/staking/aminomessages.ts
+++ b/packages/stargate/src/modules/staking/aminomessages.ts
@@ -143,7 +143,7 @@ export function isAminoMsgUndelegate(msg: AminoMsg): msg is AminoMsgUndelegate {
   return msg.type === "cosmos-sdk/MsgUndelegate";
 }
 
-export function createStakingAminoConverters(): Record<string, AminoConverter | "not_supported_by_chain"> {
+export function createStakingAminoConverters(): Record<string, AminoConverter> {
   return {
     "/cosmos.staking.v1beta1.MsgBeginRedelegate": {
       aminoType: "cosmos-sdk/MsgBeginRedelegate",