diff --git a/backend/local/backend_local.go b/backend/local/backend_local.go
index 4ac20013e..acb5215af 100644
--- a/backend/local/backend_local.go
+++ b/backend/local/backend_local.go
@@ -163,6 +163,7 @@ func (b *Local) contextFromPlanFile(pf *planfile.Reader, opts terraform.ContextO
 			errSummary,
 			fmt.Sprintf("Failed to read plan from plan file: %s.", err),
 		))
+		return nil, snap, diags
 	}
 
 	variables := terraform.InputValues{}
diff --git a/command/apply.go b/command/apply.go
index de7ca3207..36a8d5cae 100644
--- a/command/apply.go
+++ b/command/apply.go
@@ -137,6 +137,18 @@ func (c *ApplyCommand) Run(args []string) int {
 				"Failed to read plan from plan file",
 				fmt.Sprintf("Cannot read the plan from the given plan file: %s.", err),
 			))
+			c.showDiagnostics(diags)
+			return 1
+		}
+		if plan.Backend.Config == nil {
+			// Should never happen; always indicates a bug in the creation of the plan file
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"Failed to read plan from plan file",
+				fmt.Sprintf("The given plan file does not have a valid backend configuration. This is a bug in the Terraform command that generated this plan file."),
+			))
+			c.showDiagnostics(diags)
+			return 1
 		}
 		be, beDiags = c.BackendForPlan(plan.Backend)
 	}
diff --git a/command/apply_test.go b/command/apply_test.go
index 25a57ce8b..70a6b03f4 100644
--- a/command/apply_test.go
+++ b/command/apply_test.go
@@ -108,6 +108,7 @@ func TestApply_lockedState(t *testing.T) {
 
 // test apply with locked state, waiting for unlock
 func TestApply_lockedStateWait(t *testing.T) {
+	t.Fatalf("FIXME: this test seems to be making the test program prematurely exit")
 	statePath := testTempFile(t)
 
 	unlock, err := testLockState("./testdata", statePath)
diff --git a/command/state_list_test.go b/command/state_list_test.go
index 0d4cedd00..7a7a6dfe9 100644
--- a/command/state_list_test.go
+++ b/command/state_list_test.go
@@ -14,7 +14,7 @@ func TestStateList(t *testing.T) {
 	statePath := testStateFile(t, state)
 
 	p := testProvider()
-	ui := new(cli.MockUi)
+	ui := cli.NewMockUi()
 	c := &StateListCommand{
 		Meta: Meta{
 			testingOverrides: metaOverridesForProvider(p),
@@ -42,7 +42,7 @@ func TestStateListWithID(t *testing.T) {
 	statePath := testStateFile(t, state)
 
 	p := testProvider()
-	ui := new(cli.MockUi)
+	ui := cli.NewMockUi()
 	c := &StateListCommand{
 		Meta: Meta{
 			testingOverrides: metaOverridesForProvider(p),
@@ -71,7 +71,7 @@ func TestStateListWithNonExistentID(t *testing.T) {
 	statePath := testStateFile(t, state)
 
 	p := testProvider()
-	ui := new(cli.MockUi)
+	ui := cli.NewMockUi()
 	c := &StateListCommand{
 		Meta: Meta{
 			testingOverrides: metaOverridesForProvider(p),
@@ -104,7 +104,7 @@ func TestStateList_backendState(t *testing.T) {
 	defer testChdir(t, td)()
 
 	p := testProvider()
-	ui := new(cli.MockUi)
+	ui := cli.NewMockUi()
 	c := &StateListCommand{
 		Meta: Meta{
 			testingOverrides: metaOverridesForProvider(p),
@@ -130,7 +130,7 @@ func TestStateList_noState(t *testing.T) {
 	defer testFixCwd(t, tmp, cwd)
 
 	p := testProvider()
-	ui := new(cli.MockUi)
+	ui := cli.NewMockUi()
 	c := &StateListCommand{
 		Meta: Meta{
 			testingOverrides: metaOverridesForProvider(p),
diff --git a/command/state_push_test.go b/command/state_push_test.go
index e7fd5f446..21115065c 100644
--- a/command/state_push_test.go
+++ b/command/state_push_test.go
@@ -194,6 +194,7 @@ func TestStatePush_serialOlder(t *testing.T) {
 }
 
 func TestStatePush_forceRemoteState(t *testing.T) {
+	t.Fatalf("FIXME: This test seems to be getting hanged or into an infinite loop")
 	td := tempDir(t)
 	copy.CopyDir(testFixturePath("inmem-backend"), td)
 	defer os.RemoveAll(td)
diff --git a/command/state_test.go b/command/state_test.go
index 433c6336b..49762075e 100644
--- a/command/state_test.go
+++ b/command/state_test.go
@@ -6,7 +6,7 @@ import (
 	"sort"
 	"testing"
 
-	"github.com/hashicorp/terraform/state"
+	"github.com/hashicorp/terraform/states/statemgr"
 )
 
 // testStateBackups returns the list of backups in order of creation
@@ -33,7 +33,7 @@ func TestStateDefaultBackupExtension(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	backupPath := s.(*state.BackupState).Path
+	backupPath := s.(*statemgr.Filesystem).BackupPath()
 	match := regexp.MustCompile(`terraform\.tfstate\.\d+\.backup$`).MatchString
 	if !match(backupPath) {
 		t.Fatal("Bad backup path:", backupPath)
diff --git a/command/workspace_command_test.go b/command/workspace_command_test.go
index 4503850fd..146c21aba 100644
--- a/command/workspace_command_test.go
+++ b/command/workspace_command_test.go
@@ -215,6 +215,7 @@ func TestWorkspace_createInvalid(t *testing.T) {
 }
 
 func TestWorkspace_createWithState(t *testing.T) {
+	t.Fatalf("FIXME: This test seems to be getting hung or into an infinite loop")
 	td := tempDir(t)
 	copy.CopyDir(testFixturePath("inmem-backend"), td)
 	defer os.RemoveAll(td)
diff --git a/plans/planfile/tfplan.go b/plans/planfile/tfplan.go
index 0474f97e3..2db909b9f 100644
--- a/plans/planfile/tfplan.go
+++ b/plans/planfile/tfplan.go
@@ -287,6 +287,13 @@ func valueFromTfplan(rawV *planproto.DynamicValue) (plans.DynamicValue, error) {
 // writeTfplan serializes the given plan into the protobuf-based format used
 // for the "tfplan" portion of a plan file.
 func writeTfplan(plan *plans.Plan, w io.Writer) error {
+	if plan == nil {
+		return fmt.Errorf("cannot write plan file for nil plan")
+	}
+	if plan.Changes == nil {
+		return fmt.Errorf("cannot write plan file with nil changeset")
+	}
+
 	rawPlan := &planproto.Plan{
 		Version:          tfplanFormatVersion,
 		TerraformVersion: version.String(),
diff --git a/states/state.go b/states/state.go
index c6d005a11..1f842359e 100644
--- a/states/state.go
+++ b/states/state.go
@@ -47,6 +47,9 @@ func BuildState(cb func(*SyncState)) *State {
 // in the receiver. In other words, if this state could be safely replaced
 // with the return value of NewState and be functionally equivalent.
 func (s *State) Empty() bool {
+	if s == nil {
+		return true
+	}
 	for _, ms := range s.Modules {
 		if len(ms.Resources) != 0 {
 			return false
@@ -86,6 +89,9 @@ func (s *State) RemoveModule(addr addrs.ModuleInstance) {
 
 // RootModule is a convenient alias for Module(addrs.RootModuleInstance).
 func (s *State) RootModule() *Module {
+	if s == nil {
+		panic("RootModule called on nil State")
+	}
 	return s.Modules[addrs.RootModuleInstance.String()]
 }
 
diff --git a/states/statefile/marshal_equal.go b/states/statefile/marshal_equal.go
index c1d553bd2..4948b39b9 100644
--- a/states/statefile/marshal_equal.go
+++ b/states/statefile/marshal_equal.go
@@ -17,6 +17,11 @@ func StatesMarshalEqual(a, b *states.State) bool {
 	var aBuf bytes.Buffer
 	var bBuf bytes.Buffer
 
+	// nil states are not valid states, and so they can never martial equal.
+	if a == nil || b == nil {
+		return false
+	}
+
 	// We write here some temporary files that have no header information
 	// populated, thus ensuring that we're only comparing the state itself
 	// and not any metadata.
diff --git a/states/statefile/version4.go b/states/statefile/version4.go
index 1b82bf702..ee8b65236 100644
--- a/states/statefile/version4.go
+++ b/states/statefile/version4.go
@@ -298,6 +298,9 @@ func writeStateV4(file *File, w io.Writer) tfdiags.Diagnostics {
 	// read/prepare V4 functions above would stick around.
 
 	var diags tfdiags.Diagnostics
+	if file == nil || file.State == nil {
+		panic("attempt to write nil state to file")
+	}
 
 	var terraformVersion string
 	if file.TerraformVersion != nil {
diff --git a/states/statemgr/filesystem.go b/states/statemgr/filesystem.go
index bbb03dad7..51cc31037 100644
--- a/states/statemgr/filesystem.go
+++ b/states/statemgr/filesystem.go
@@ -101,6 +101,12 @@ func (s *Filesystem) SetBackupPath(path string) {
 	s.writtenBackup = false
 }
 
+// BackupPath returns the manager's backup path if backup files are enabled,
+// or an empty string otherwise.
+func (s *Filesystem) BackupPath() string {
+	return s.backupPath
+}
+
 // State is an implementation of Reader.
 func (s *Filesystem) State() *states.State {
 	defer s.mutex()()