diff --git a/CHANGELOG.md b/CHANGELOG.md
index 991139534087..c21780ebd166 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (baseapp) [#2](https://github.com/01builders/cosmos-sdk/pull/2) Re-add query router for custom abci queries.
 * (x/auth/vesting) [#3](https://github.com/01builders/cosmos-sdk/pull/3) Add start time for continuous vesting accounts.
 * (testing) [#5](https://github.com/01builders/cosmos-sdk/pull/5) Add `MakeTestEncodingConfigWithOpts` to pass `testutil.CodecOptions` when creating `TestEncodingConfig`.
+* (x/auth) [#6](https://github.com/01builders/cosmos-sdk/pull/6) Support legacy global AccountNumber.
 
 ## [v0.50.11](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.50.11) - 2024-12-16
 
diff --git a/x/auth/keeper/keeper.go b/x/auth/keeper/keeper.go
index 393ed99907d3..1e1ffa7dfc36 100644
--- a/x/auth/keeper/keeper.go
+++ b/x/auth/keeper/keeper.go
@@ -17,6 +17,7 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 	"github.com/cosmos/cosmos-sdk/x/auth/types"
+	gogotypes "github.com/cosmos/gogoproto/types"
 )
 
 // AccountKeeperI is the interface contract that x/auth's keeper implements.
@@ -179,13 +180,45 @@ func (ak AccountKeeper) GetSequence(ctx context.Context, addr sdk.AccAddress) (u
 	return acc.GetSequence(), nil
 }
 
+func (ak AccountKeeper) NextAccountNumberLegacy(ctx context.Context) (uint64, error) {
+	store := ak.storeService.OpenKVStore(ctx)
+	b, err := store.Get(types.LegacyGlobalAccountNumberKey)
+	if err != nil {
+		return 0, fmt.Errorf("failed to get legacy account number: %w", err)
+	}
+	v := new(gogotypes.UInt64Value)
+	if err := v.Unmarshal(b); err != nil {
+		return 0, fmt.Errorf("failed to unmarshal legacy account number: %w", err)
+	}
+	if err := ak.AccountNumber.Set(ctx, v.Value+1); err != nil {
+		return 0, fmt.Errorf("failed to set account number: %w", err)
+	}
+
+	return v.Value, nil
+}
+
 // NextAccountNumber returns and increments the global account number counter.
 // If the global account number is not set, it initializes it with value 0.
 func (ak AccountKeeper) NextAccountNumber(ctx context.Context) uint64 {
-	n, err := ak.AccountNumber.Next(ctx)
+	n, err := collections.Item[uint64](ak.AccountNumber).Get(ctx)
+	if err == nil {
+		if err := ak.AccountNumber.Set(ctx, n+1); err != nil {
+			panic(err)
+		}
+		return n
+	}
+
+	if errors.Is(err, collections.ErrNotFound) {
+		// this won't happen in the tip of production network,
+		// but can happen when query historical states,
+		// fallback to old key for backward-compatibility.
+		n, err = ak.NextAccountNumberLegacy(ctx)
+	}
+
 	if err != nil {
 		panic(err)
 	}
+
 	return n
 }
 
diff --git a/x/auth/migrations/v5/migrate.go b/x/auth/migrations/v5/migrate.go
index 44fcf970c359..d0d4ee981b8a 100644
--- a/x/auth/migrations/v5/migrate.go
+++ b/x/auth/migrations/v5/migrate.go
@@ -7,13 +7,12 @@ import (
 
 	"cosmossdk.io/collections"
 	storetypes "cosmossdk.io/core/store"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 )
 
-var LegacyGlobalAccountNumberKey = []byte("globalAccountNumber")
-
 func Migrate(ctx context.Context, storeService storetypes.KVStoreService, sequence collections.Sequence) error {
 	store := storeService.OpenKVStore(ctx)
-	b, err := store.Get(LegacyGlobalAccountNumberKey)
+	b, err := store.Get(authtypes.LegacyGlobalAccountNumberKey)
 	if err != nil {
 		return err
 	}
@@ -37,7 +36,7 @@ func Migrate(ctx context.Context, storeService storetypes.KVStoreService, sequen
 	}
 
 	// remove the value from the old prefix.
-	err = store.Delete(LegacyGlobalAccountNumberKey)
+	err = store.Delete(authtypes.LegacyGlobalAccountNumberKey)
 	if err != nil {
 		return err
 	}
diff --git a/x/auth/migrations/v5/migrate_test.go b/x/auth/migrations/v5/migrate_test.go
index c0c7113fb580..3c1ee663e385 100644
--- a/x/auth/migrations/v5/migrate_test.go
+++ b/x/auth/migrations/v5/migrate_test.go
@@ -8,6 +8,7 @@ import (
 
 	"cosmossdk.io/collections"
 	"cosmossdk.io/collections/colltest"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 )
 
 func TestMigrate(t *testing.T) {
@@ -21,7 +22,7 @@ func TestMigrate(t *testing.T) {
 	legacySeqBytes, err := (&types.UInt64Value{Value: wantValue}).Marshal()
 	require.NoError(t, err)
 
-	err = kv.OpenKVStore(ctx).Set(LegacyGlobalAccountNumberKey, legacySeqBytes)
+	err = kv.OpenKVStore(ctx).Set(authtypes.LegacyGlobalAccountNumberKey, legacySeqBytes)
 	require.NoError(t, err)
 
 	err = Migrate(ctx, kv, seq)
diff --git a/x/auth/types/keys.go b/x/auth/types/keys.go
index fb3295511f23..cd3af0ad0b3e 100644
--- a/x/auth/types/keys.go
+++ b/x/auth/types/keys.go
@@ -28,4 +28,7 @@ var (
 
 	// AccountNumberStoreKeyPrefix prefix for account-by-id store
 	AccountNumberStoreKeyPrefix = collections.NewPrefix("accountNumber")
+
+	// legacy param key for global account number
+	LegacyGlobalAccountNumberKey = []byte("globalAccountNumber")
 )