diff --git a/encoding/jsonschema/decode.go b/encoding/jsonschema/decode.go
index bf58b4b..ac2a4af 100644
--- a/encoding/jsonschema/decode.go
+++ b/encoding/jsonschema/decode.go
@@ -380,8 +380,9 @@
 			// Convert each constraint into a either a value or a functor.
 			c := constraintMap[key]
 			if c == nil {
-				if pass == 0 {
-					s.warnf(n.Pos(), "unsupported constraint %q", key)
+				if pass == 0 && s.cfg.Strict {
+					// TODO: value is not the correct possition, albeit close. Fix this.
+					s.warnf(value.Pos(), "unsupported constraint %q", key)
 				}
 				return
 			}
diff --git a/encoding/jsonschema/jsonschema.go b/encoding/jsonschema/jsonschema.go
index 09e4173..5f5791b 100644
--- a/encoding/jsonschema/jsonschema.go
+++ b/encoding/jsonschema/jsonschema.go
@@ -57,7 +57,8 @@
 type Config struct {
 	PkgName string
 
-	ID string // URL of the original source, corresponding to the $id field.
+	// ID sets the URL of the original source, corresponding to the $id field.
+	ID string
 
 	// JSON reference of location containing schema. The empty string indicates
 	// that there is a single schema at the root.
@@ -81,5 +82,9 @@
 	// - selection and definition of formats
 	// - documentation hooks.
 
+	// Strict reports an error for unsupported features, rather than ignoring
+	// them.
+	Strict bool
+
 	_ struct{} // prohibit casting from different type.
 }
diff --git a/encoding/jsonschema/testdata/unsupported.txtar b/encoding/jsonschema/testdata/unsupported.txtar
new file mode 100644
index 0000000..b2b3449
--- /dev/null
+++ b/encoding/jsonschema/testdata/unsupported.txtar
@@ -0,0 +1,49 @@
+-- unsupported.json --
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "definitions": {
+    "ref": {
+      "properties": {
+        "branches": {
+          "type": "object"
+        },
+        "branches-ignore": {
+          "type": "object"
+        }
+      },
+      "oneOf": [
+        {
+          "type": "object",
+          "allOf": [
+            {
+              "not": {
+                "required": [
+                  "branches",
+                  "branches-ignore"
+                ]
+              }
+            }
+          ]
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  }
+}
+
+
+-- out.cue --
+Schema :: _ @jsonschema(schema="http://json-schema.org/draft-07/schema")
+Schema :: _
+
+def: ref :: null | {
+	branches?: {
+		...
+	}
+	"branches-ignore"?: {
+		...
+	}
+	...
+}