diff --git a/node-tools/internal/approval/approval_test.go b/node-tools/internal/approval/approval_test.go
index 53dfe47..77cbc66 100644
--- a/node-tools/internal/approval/approval_test.go
+++ b/node-tools/internal/approval/approval_test.go
@@ -390,6 +390,18 @@ func TestTheRefusalsAndAnswers(t *testing.T) {
 				t.Fatalf("marked: %v, runs %d", err, w.runs)
 			}
 		}},
+		{"§13: the fixture state refuses a key the bus refuses, so every key the gate writes here is one the bus holds (A-209)", func(t *testing.T, w *world) {
+			if _, err := w.state.Put("n1.act.sha256:00", "x"); err == nil {
+				t.Fatal("the fixture state held a key with a colon, which the bus refuses")
+			}
+			if _, err := w.state.Create("n1..ask", "x"); err == nil {
+				t.Fatal("the fixture state held a key with an empty name")
+			}
+			_, _ = w.do(call("wipe", `{"dir":"scratch"}`))
+			if len(w.asked) != 1 || len(w.state.Vals) == 0 {
+				t.Fatalf("the gate kept nothing through the fixture state: asked %d, keys %d", len(w.asked), len(w.state.Vals))
+			}
+		}},
 		{"§13: an ask over 256 KiB is refused naming the cause", func(t *testing.T, w *world) {
 			c := call("wipe", `{}`)
 			c.Description = strings.Repeat("w", 300*1024)
diff --git a/node-tools/internal/meshtest/state.go b/node-tools/internal/meshtest/state.go
index 87c9e4d..4ec6417 100644
--- a/node-tools/internal/meshtest/state.go
+++ b/node-tools/internal/meshtest/state.go
@@ -2,14 +2,18 @@ package meshtest
 
 import (
 	"encoding/json"
+	"fmt"
 	"sort"
+	"strings"
 	"sync"
 
 	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/keys"
 )
 
 // State is a module's state as a fixture, the shape a gate's Store takes: Fail makes every read and write fail, as a bus
-// refusing them; Vals are its values by key.
+// refusing them; Vals are its values by key. A key the bus refuses (a name outside letters, digits and -/_=, in
+// dot-separated names) is refused here too, so no test passes a key the live bus refuses (lead answer A-209).
 type State struct {
 	mu   sync.Mutex
 	Vals map[string]json.RawMessage
@@ -18,12 +22,25 @@ type State struct {
 	Fail error
 }
 
+// checkKey refuses a key the bus would.
+func checkKey(k string) error {
+	for _, part := range strings.Split(k, ".") {
+		if keys.CheckName("key", part) != nil {
+			return fmt.Errorf("%q is not a key the bus can hold: letters, digits and -/_=, in dot-separated names", k)
+		}
+	}
+	return nil
+}
+
 // NewState is an empty State.
 func NewState() *State { return &State{Vals: map[string]json.RawMessage{}, revs: map[string]uint64{}} }
 
 func (m *State) Get(k string) (*stdio.StateEntry, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
+	if err := checkKey(k); err != nil {
+		return nil, err
+	}
 	if m.Fail != nil {
 		return nil, m.Fail
 	}
@@ -36,6 +53,9 @@ func (m *State) Get(k string) (*stdio.StateEntry, error) {
 func (m *State) Create(k string, v any) (uint64, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
+	if err := checkKey(k); err != nil {
+		return 0, err
+	}
 	if m.Fail != nil {
 		return 0, m.Fail
 	}
@@ -47,6 +67,9 @@ func (m *State) Create(k string, v any) (uint64, error) {
 func (m *State) Update(k string, v any, rev uint64) (uint64, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
+	if err := checkKey(k); err != nil {
+		return 0, err
+	}
 	if m.Fail != nil {
 		return 0, m.Fail
 	}
@@ -58,6 +81,9 @@ func (m *State) Update(k string, v any, rev uint64) (uint64, error) {
 func (m *State) Put(k string, v any) (uint64, error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
+	if err := checkKey(k); err != nil {
+		return 0, err
+	}
 	if m.Fail != nil {
 		return 0, m.Fail
 	}