diff --git a/CHANGELOG.md b/CHANGELOG.md
index 14b54ec6d12c..cb6bfb4f6822 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -94,6 +94,8 @@ to now accept a `codec.JSONMarshaler` for modular serialization of genesis state
 * (modules) [\#5569](https://github.com/cosmos/cosmos-sdk/issues/5569) `InitGenesis`, for the relevant modules, now ensures module accounts exist.
 * (crypto/keyring) [\#5844](https://github.com/cosmos/cosmos-sdk/pull/5844) Keybase/Keyring `Sign()` methods no longer decode amino signatures
 when method receivers are offline/multisig keys.
+* (x/auth) [\#5892](https://github.com/cosmos/cosmos-sdk/pull/5892) Add `RegisterKeyTypeCodec` to register new
+types (eg. keys) to the `auth` module internal amino codec.
 
 ### State Machine Breaking
 
diff --git a/x/auth/types/account.go b/x/auth/types/account.go
index bae7d8f3b4fe..8be072d1d169 100644
--- a/x/auth/types/account.go
+++ b/x/auth/types/account.go
@@ -8,7 +8,6 @@ import (
 	"github.com/tendermint/tendermint/crypto"
 	yaml "gopkg.in/yaml.v2"
 
-	"github.com/cosmos/cosmos-sdk/codec"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/auth/exported"
 )
@@ -61,7 +60,7 @@ func (acc BaseAccount) GetPubKey() (pk crypto.PubKey) {
 		return nil
 	}
 
-	codec.Cdc.MustUnmarshalBinaryBare(acc.PubKey, &pk)
+	amino.MustUnmarshalBinaryBare(acc.PubKey, &pk)
 	return pk
 }
 
diff --git a/x/auth/types/codec.go b/x/auth/types/codec.go
index be7f21b3f1d1..53de61568a1a 100644
--- a/x/auth/types/codec.go
+++ b/x/auth/types/codec.go
@@ -26,6 +26,13 @@ func RegisterCodec(cdc *codec.Codec) {
 	cdc.RegisterConcrete(StdTx{}, "cosmos-sdk/StdTx", nil)
 }
 
+// RegisterKeyTypeCodec registers an external concrete type defined in
+// another module for the internal ModuleCdc.
+func RegisterKeyTypeCodec(o interface{}, name string) {
+	amino.RegisterConcrete(o, name, nil)
+	ModuleCdc = codec.NewHybridCodec(amino)
+}
+
 var (
 	amino = codec.New()
 
@@ -41,5 +48,4 @@ var (
 func init() {
 	RegisterCodec(amino)
 	codec.RegisterCrypto(amino)
-	amino.Seal()
 }
diff --git a/x/auth/types/stdtx.go b/x/auth/types/stdtx.go
index 04e9ec1fdd79..786d8ffde979 100644
--- a/x/auth/types/stdtx.go
+++ b/x/auth/types/stdtx.go
@@ -79,7 +79,7 @@ func (ss StdSignature) GetPubKey() (pk crypto.PubKey) {
 		return nil
 	}
 
-	codec.Cdc.MustUnmarshalBinaryBare(ss.PubKey, &pk)
+	amino.MustUnmarshalBinaryBare(ss.PubKey, &pk)
 	return pk
 }