diff --git a/encoding/jsonschema/generate.go b/encoding/jsonschema/generate.go
index a434f9fe1..28ba2fbff 100644
--- a/encoding/jsonschema/generate.go
+++ b/encoding/jsonschema/generate.go
@@ -291,6 +291,12 @@ func (g *generator) makeItem0(v cue.Value, mode closedMode) item {
 		if !pkg.Exists() {
 			break
 		}
+		// Check if this is a reference to a known validator function.
+		// For example, list.UniqueItems (without parens) should be treated
+		// the same as list.UniqueItems().
+		if it := g.makeCallItem(v, []cue.Value{v}, mode); it != nil {
+			return it
+		}
 		// It's a reference: generate a definition for it.
 		// TODO Not all references need or should have a definition.
 		if name := g.cfg.NameFunc(pkg, path); name != "" {
@@ -422,7 +428,12 @@ func (g *generator) makeItem0(v cue.Value, mode closedMode) item {
 			return &itemFalse{}
 		}
 	case cue.CallOp:
-		return g.makeCallItem(v, args, mode)
+		if it := g.makeCallItem(v, args, mode); it != nil {
+			return it
+		}
+		// For unknown functions, accept anything rather than fail.
+		// This allows for gradual implementation of more function types.
+		return &itemTrue{}
 	}
 	if !v.IsNull() {
 		// We want to encode null as {type: "null"} not {const: null}
@@ -864,9 +875,7 @@ func (g *generator) makeCallItem(v cue.Value, args []cue.Value, mode closedMode)
 		}
 
 	default:
-		// For unknown functions, accept anything rather than fail.
-		// This allows for gradual implementation of more function types
-		return &itemTrue{}
+		return nil
 	}
 }
 
diff --git a/encoding/jsonschema/testdata/generate/uniqueitems.txtar b/encoding/jsonschema/testdata/generate/uniqueitems.txtar
index b31c848bb..2a6bfcc31 100644
--- a/encoding/jsonschema/testdata/generate/uniqueitems.txtar
+++ b/encoding/jsonschema/testdata/generate/uniqueitems.txtar
@@ -7,8 +7,6 @@ uniqueList?: list.UniqueItems()
 
 uniqueListNoCall?: list.UniqueItems
 
-// TODO this doesn't work - the code currently just looks
-// for call expressions but this isn't a call expression.
 uniqueBools?: list.UniqueItems() & [bool, bool]
 
 -- datatest/tests.cue --
@@ -27,8 +25,7 @@ badUnique: {
 
 badUniqueNoCall: {
 	data: uniqueListNoCall: [1, 1, 2]
-	// TODO this should be an error.
-	//error: true
+	error: true
 }
 
 badUniqueBools: {
@@ -38,12 +35,7 @@ badUniqueBools: {
 -- out/generate-v3/schema --
 {
 	$schema: "https://json-schema.org/draft/2020-12/schema"
-	$defs: {
-		UniqueItems: {
-			type: "array"
-		}
-	}
-	type: "object"
+	type:    "object"
 	properties: {
 		uniqueBools: {
 			type: "array"
@@ -61,18 +53,22 @@ badUniqueBools: {
 			uniqueItems: true
 		}
 		uniqueListNoCall: {
-			$ref: "#/$defs/UniqueItems"
+			type:        "array"
+			uniqueItems: true
 		}
 	}
 }
 -- out/generate-v3/ok --
 -- out/generate-v3/badUnique --
 badUnique.data.uniqueList: invalid value [1,1,2] (does not satisfy list.UniqueItems): equal value (1) at position 0 and 1:
-    1:289
+    1:248
     ./datatest/tests.cue:10:20
 -- out/generate-v3/badUniqueBools --
 badUniqueBools.data.uniqueBools: invalid value [true,true] (does not satisfy list.UniqueItems): equal value (true) at position 0 and 1:
-    1:240
-    ./datatest/tests.cue:21:21
-    1:214
+    1:199
+    ./datatest/tests.cue:20:21
+    1:173
 -- out/generate-v3/badUniqueNoCall --
+badUniqueNoCall.data.uniqueListNoCall: invalid value [1,1,2] (does not satisfy list.UniqueItems): equal value (1) at position 0 and 1:
+    1:303
+    ./datatest/tests.cue:15:26