diff --git a/backend/atlas/backend.go b/backend/atlas/backend.go
index e4f247455..9cd15d424 100644
--- a/backend/atlas/backend.go
+++ b/backend/atlas/backend.go
@@ -12,7 +12,6 @@ import (
 
 	"github.com/hashicorp/terraform/backend"
 	"github.com/hashicorp/terraform/configs/configschema"
-	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/hashicorp/terraform/state"
 	"github.com/hashicorp/terraform/state/remote"
 	"github.com/hashicorp/terraform/terraform"
@@ -43,9 +42,6 @@ type Backend struct {
 	// stateClient is the legacy state client, setup in Configure
 	stateClient *stateClient
 
-	// schema is the schema for configuration, set by init
-	schema *schema.Backend
-
 	// opLock locks operations
 	opLock sync.Mutex
 }
@@ -79,7 +75,7 @@ func (b *Backend) ConfigSchema() *configschema.Block {
 	}
 }
 
-func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Backend) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 
 	name := obj.GetAttr("name").AsString()
@@ -105,7 +101,7 @@ func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		}
 	}
 
-	return diags
+	return obj, diags
 }
 
 func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
@@ -116,7 +112,7 @@ func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
 		RunId: os.Getenv("ATLAS_RUN_ID"),
 	}
 
-	name := obj.GetAttr("name").AsString() // assumed valid due to ValidateConfig method
+	name := obj.GetAttr("name").AsString() // assumed valid due to PrepareConfig method
 	slashIdx := strings.Index(name, "/")
 	client.User = name[:slashIdx]
 	client.Name = name[slashIdx+1:]
@@ -139,7 +135,7 @@ func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
 		addr := v.AsString()
 		addrURL, err := url.Parse(addr)
 		if err != nil {
-			// We already validated the URL in ValidateConfig, so this shouldn't happen
+			// We already validated the URL in PrepareConfig, so this shouldn't happen
 			panic(err)
 		}
 		client.Server = addr
diff --git a/backend/backend.go b/backend/backend.go
index 5259af8ad..6f220b6b5 100644
--- a/backend/backend.go
+++ b/backend/backend.go
@@ -59,9 +59,10 @@ type Backend interface {
 	// be safely used before configuring.
 	ConfigSchema() *configschema.Block
 
-	// ValidateConfig checks the validity of the values in the given
-	// configuration, assuming that its structure has already been validated
-	// per the schema returned by ConfigSchema.
+	// PrepareConfig checks the validity of the values in the given
+	// configuration, and inserts any missing defaults, assuming that its
+	// structure has already been validated per the schema returned by
+	// ConfigSchema.
 	//
 	// This method does not have any side-effects for the backend and can
 	// be safely used before configuring. It also does not consult any
@@ -76,14 +77,14 @@ type Backend interface {
 	// as tfdiags.AttributeValue, and so the caller should provide the
 	// necessary context via the diags.InConfigBody method before returning
 	// diagnostics to the user.
-	ValidateConfig(cty.Value) tfdiags.Diagnostics
+	PrepareConfig(cty.Value) (cty.Value, tfdiags.Diagnostics)
 
 	// Configure uses the provided configuration to set configuration fields
 	// within the backend.
 	//
 	// The given configuration is assumed to have already been validated
 	// against the schema returned by ConfigSchema and passed validation
-	// via ValidateConfig.
+	// via PrepareConfig.
 	//
 	// This method may be called only once per backend instance, and must be
 	// called before all other methods except where otherwise stated.
diff --git a/backend/init/deprecate_test.go b/backend/init/deprecate_test.go
index 61d252a0d..c45d62d2b 100644
--- a/backend/init/deprecate_test.go
+++ b/backend/init/deprecate_test.go
@@ -14,7 +14,7 @@ func TestDeprecateBackend(t *testing.T) {
 		deprecateMessage,
 	)
 
-	diags := deprecatedBackend.ValidateConfig(cty.EmptyObjectVal)
+	_, diags := deprecatedBackend.PrepareConfig(cty.EmptyObjectVal)
 	if len(diags) != 1 {
 		t.Errorf("got %d diagnostics; want 1", len(diags))
 		for _, diag := range diags {
diff --git a/backend/init/init.go b/backend/init/init.go
index 1ee473401..f11755c22 100644
--- a/backend/init/init.go
+++ b/backend/init/init.go
@@ -108,11 +108,11 @@ type deprecatedBackendShim struct {
 	Message string
 }
 
-// ValidateConfig delegates to the wrapped backend to validate its config
+// PrepareConfig delegates to the wrapped backend to validate its config
 // and then appends shim's deprecation warning.
-func (b deprecatedBackendShim) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
-	diags := b.Backend.ValidateConfig(obj)
-	return diags.Append(tfdiags.SimpleWarning(b.Message))
+func (b deprecatedBackendShim) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
+	newObj, diags := b.Backend.PrepareConfig(obj)
+	return newObj, diags.Append(tfdiags.SimpleWarning(b.Message))
 }
 
 // DeprecateBackend can be used to wrap a backend to retrun a deprecation
diff --git a/backend/local/backend.go b/backend/local/backend.go
index 8a4050362..54cab6ecb 100644
--- a/backend/local/backend.go
+++ b/backend/local/backend.go
@@ -139,9 +139,9 @@ func (b *Local) ConfigSchema() *configschema.Block {
 	}
 }
 
-func (b *Local) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Local) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	if b.Backend != nil {
-		return b.Backend.ValidateConfig(obj)
+		return b.Backend.PrepareConfig(obj)
 	}
 
 	var diags tfdiags.Diagnostics
@@ -170,7 +170,7 @@ func (b *Local) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		}
 	}
 
-	return diags
+	return obj, diags
 }
 
 func (b *Local) Configure(obj cty.Value) tfdiags.Diagnostics {
diff --git a/backend/nil.go b/backend/nil.go
index 6f4d876ab..8c46f49d0 100644
--- a/backend/nil.go
+++ b/backend/nil.go
@@ -17,8 +17,8 @@ func (Nil) ConfigSchema() *configschema.Block {
 	return &configschema.Block{}
 }
 
-func (Nil) ValidateConfig(cty.Value) tfdiags.Diagnostics {
-	return nil
+func (Nil) PrepareConfig(v cty.Value) (cty.Value, tfdiags.Diagnostics) {
+	return v, nil
 }
 
 func (Nil) Configure(cty.Value) tfdiags.Diagnostics {
diff --git a/backend/remote-state/s3/backend_test.go b/backend/remote-state/s3/backend_test.go
index 3fc939c80..a24325880 100644
--- a/backend/remote-state/s3/backend_test.go
+++ b/backend/remote-state/s3/backend_test.go
@@ -76,7 +76,7 @@ func TestBackendConfig_invalidKey(t *testing.T) {
 		"dynamodb_table": "dynamoTable",
 	})
 
-	diags := New().ValidateConfig(cfg)
+	_, diags := New().PrepareConfig(cfg)
 	if !diags.HasErrors() {
 		t.Fatal("expected config validation error")
 	}
diff --git a/backend/remote/backend.go b/backend/remote/backend.go
index f4fd3eb5b..d0f808c2c 100644
--- a/backend/remote/backend.go
+++ b/backend/remote/backend.go
@@ -139,8 +139,8 @@ func (b *Remote) ConfigSchema() *configschema.Block {
 	}
 }
 
-// ValidateConfig implements backend.Enhanced.
-func (b *Remote) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+// PrepareConfig implements backend.Backend.
+func (b *Remote) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 
 	if val := obj.GetAttr("organization"); val.IsNull() || val.AsString() == "" {
@@ -182,7 +182,7 @@ func (b *Remote) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 		))
 	}
 
-	return diags
+	return obj, diags
 }
 
 // Configure implements backend.Enhanced.
diff --git a/backend/remote/backend_test.go b/backend/remote/backend_test.go
index c7f16fc45..ac3fd01eb 100644
--- a/backend/remote/backend_test.go
+++ b/backend/remote/backend_test.go
@@ -117,7 +117,7 @@ func TestRemote_config(t *testing.T) {
 		b := New(testDisco(s))
 
 		// Validate
-		valDiags := b.ValidateConfig(tc.config)
+		_, valDiags := b.PrepareConfig(tc.config)
 		if (valDiags.Err() != nil || tc.valErr != "") &&
 			(valDiags.Err() == nil || !strings.Contains(valDiags.Err().Error(), tc.valErr)) {
 			t.Fatalf("%s: unexpected validation result: %v", name, valDiags.Err())
@@ -196,7 +196,7 @@ func TestRemote_versionConstraints(t *testing.T) {
 		version.Version = tc.version
 
 		// Validate
-		valDiags := b.ValidateConfig(tc.config)
+		_, valDiags := b.PrepareConfig(tc.config)
 		if valDiags.HasErrors() {
 			t.Fatalf("%s: unexpected validation result: %v", name, valDiags.Err())
 		}
diff --git a/backend/remote/testing.go b/backend/remote/testing.go
index 7d05f64dc..09c541897 100644
--- a/backend/remote/testing.go
+++ b/backend/remote/testing.go
@@ -97,10 +97,11 @@ func testBackend(t *testing.T, obj cty.Value) (*Remote, func()) {
 	b := New(testDisco(s))
 
 	// Configure the backend so the client is created.
-	valDiags := b.ValidateConfig(obj)
+	newObj, valDiags := b.PrepareConfig(obj)
 	if len(valDiags) != 0 {
 		t.Fatal(valDiags.ErrWithWarnings())
 	}
+	obj = newObj
 
 	confDiags := b.Configure(obj)
 	if len(confDiags) != 0 {
diff --git a/backend/testing.go b/backend/testing.go
index d44073ad9..79980debf 100644
--- a/backend/testing.go
+++ b/backend/testing.go
@@ -39,13 +39,15 @@ func TestBackendConfig(t *testing.T, b Backend, c hcl.Body) Backend {
 	obj, decDiags := hcldec.Decode(c, spec, nil)
 	diags = diags.Append(decDiags)
 
-	valDiags := b.ValidateConfig(obj)
+	newObj, valDiags := b.PrepareConfig(obj)
 	diags = diags.Append(valDiags.InConfigBody(c))
 
 	if len(diags) != 0 {
 		t.Fatal(diags.ErrWithWarnings())
 	}
 
+	obj = newObj
+
 	confDiags := b.Configure(obj)
 	if len(confDiags) != 0 {
 		confDiags = confDiags.InConfigBody(c)
diff --git a/builtin/providers/terraform/data_source_state.go b/builtin/providers/terraform/data_source_state.go
index 194309bd3..765437231 100644
--- a/builtin/providers/terraform/data_source_state.go
+++ b/builtin/providers/terraform/data_source_state.go
@@ -92,11 +92,12 @@ func dataSourceRemoteStateRead(d *cty.Value) (cty.Value, tfdiags.Diagnostics) {
 		return cty.NilVal, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return cty.NilVal, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	if configureDiags.HasErrors() {
diff --git a/command/init.go b/command/init.go
index aa60cdeee..1801e1a51 100644
--- a/command/init.go
+++ b/command/init.go
@@ -446,6 +446,7 @@ func (c *InitCommand) initBackend(root *configs.Module, extraConfig rawFlags) (b
 		ConfigOverride: backendConfigOverride,
 		Init:           true,
 	}
+
 	back, backDiags := c.Backend(opts)
 	diags = diags.Append(backDiags)
 	return back, true, diags
diff --git a/command/meta_backend.go b/command/meta_backend.go
index c34d8ade4..47ea97a76 100644
--- a/command/meta_backend.go
+++ b/command/meta_backend.go
@@ -180,11 +180,12 @@ func (m *Meta) BackendForPlan(settings plans.Backend) (backend.Enhanced, tfdiags
 		return nil, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags)
@@ -917,11 +918,13 @@ func (m *Meta) backend_C_r_S_unchanged(c *configs.Backend, cHash int, sMgr *stat
 	}
 
 	// Validate the config and then configure the backend
-	validDiags := b.ValidateConfig(configVal)
+	newVal, validDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validDiags)
 	if validDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
+
 	configDiags := b.Configure(configVal)
 	diags = diags.Append(configDiags)
 	if configDiags.HasErrors() {
@@ -1037,11 +1040,12 @@ func (m *Meta) backendInitFromConfig(c *configs.Backend) (backend.Backend, cty.V
 		}
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags.InConfigBody(c.Config))
 	if validateDiags.HasErrors() {
 		return nil, cty.NilVal, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags.InConfigBody(c.Config))
@@ -1067,11 +1071,12 @@ func (m *Meta) backendInitFromSaved(s *terraform.BackendState) (backend.Backend,
 		return nil, diags
 	}
 
-	validateDiags := b.ValidateConfig(configVal)
+	newVal, validateDiags := b.PrepareConfig(configVal)
 	diags = diags.Append(validateDiags)
 	if validateDiags.HasErrors() {
 		return nil, diags
 	}
+	configVal = newVal
 
 	configureDiags := b.Configure(configVal)
 	diags = diags.Append(configureDiags)
diff --git a/helper/schema/backend.go b/helper/schema/backend.go
index eef6bee3d..d88757459 100644
--- a/helper/schema/backend.go
+++ b/helper/schema/backend.go
@@ -49,9 +49,9 @@ func (b *Backend) ConfigSchema() *configschema.Block {
 	return b.CoreConfigSchema()
 }
 
-func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
+func (b *Backend) PrepareConfig(obj cty.Value) (cty.Value, tfdiags.Diagnostics) {
 	if b == nil {
-		return nil
+		return obj, nil
 	}
 
 	var diags tfdiags.Diagnostics
@@ -63,7 +63,7 @@ func (b *Backend) ValidateConfig(obj cty.Value) tfdiags.Diagnostics {
 	for _, err := range errs {
 		diags = diags.Append(err)
 	}
-	return diags
+	return obj, diags
 }
 
 func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
diff --git a/helper/schema/backend_test.go b/helper/schema/backend_test.go
index 85ef6408c..3517aee73 100644
--- a/helper/schema/backend_test.go
+++ b/helper/schema/backend_test.go
@@ -48,7 +48,7 @@ func TestBackendValidate(t *testing.T) {
 
 	for i, tc := range cases {
 		t.Run(fmt.Sprintf("%d-%s", i, tc.Name), func(t *testing.T) {
-			diags := tc.B.ValidateConfig(cty.ObjectVal(tc.Config))
+			_, diags := tc.B.PrepareConfig(cty.ObjectVal(tc.Config))
 			if diags.HasErrors() != tc.Err {
 				t.Errorf("wrong number of diagnostics")
 			}