diff --git a/encoding/jsonschema/decode_test.go b/encoding/jsonschema/decode_test.go
index 3c9f09bdc..16f2f9fd0 100644
--- a/encoding/jsonschema/decode_test.go
+++ b/encoding/jsonschema/decode_test.go
@@ -79,6 +79,7 @@ func TestDecode(t *testing.T) {
 				// OpenAPI doesn't have a JSON Schema URI so it gets a special case.
 				cfg.DefaultVersion = jsonschema.VersionOpenAPI
 				cfg.Root = "#/components/schemas/"
+				cfg.StrictKeywords = true // OpenAPI always uses strict keywords
 				cfg.Map = func(p token.Pos, a []string) ([]ast.Label, error) {
 					// Just for testing: does not validate the path.
 					return []ast.Label{ast.NewIdent("#" + a[len(a)-1])}, nil
@@ -90,7 +91,7 @@ func TestDecode(t *testing.T) {
 			}
 		}
 		cfg.Strict = t.HasTag("strict")
-		cfg.StrictKeywords = t.HasTag("strictKeywords")
+		cfg.StrictKeywords = cfg.StrictKeywords || t.HasTag("strictKeywords")
 		cfg.StrictFeatures = t.HasTag("strictFeatures")
 
 		ctx := t.CueContext()
diff --git a/encoding/jsonschema/testdata/txtar/openapi_date-time.txtar b/encoding/jsonschema/testdata/txtar/openapi_date-time.txtar
new file mode 100644
index 000000000..b60f017f0
--- /dev/null
+++ b/encoding/jsonschema/testdata/txtar/openapi_date-time.txtar
@@ -0,0 +1,13 @@
+#version: openapi
+
+-- schema.yaml --
+components:
+  schemas:
+    DateTime:
+        type: string
+        format: date-time
+
+-- out/decode/extract --
+ERROR:
+unknown format "date-time":
+    schema.yaml:5:9