diff --git a/pkg/template/artifact.go b/pkg/template/artifact.go
index 39c0131..94008d8 100644
--- a/pkg/template/artifact.go
+++ b/pkg/template/artifact.go
@@ -220,7 +220,7 @@ func parseFunction(v any) (*Function, error) {
 			return nil, err
 		}
 		for _, in := range c.Inputs {
-			if !slices.Contains(scalarTypes, in.Type) {
+			if !validType(in.Type, nil) {
 				return nil, invalid("unsupported arkade input type %q", in.Type)
 			}
 		}
diff --git a/pkg/template/artifact_test.go b/pkg/template/artifact_test.go
index 67fd389..950cf52 100644
--- a/pkg/template/artifact_test.go
+++ b/pkg/template/artifact_test.go
@@ -267,3 +267,19 @@ func fnOf(m map[string]any, i int) map[string]any {
 func leafOf(m map[string]any, f int) map[string]any {
 	return fnOf(m, f)["leaves"].([]any)[0].(map[string]any)
 }
+
+func TestParseArtifactArrayInput(t *testing.T) {
+	doc := func(typ string) string {
+		return `{"contractName":"C","constructorInputs":[{"name":"k","type":"pubkey"}],"functions":[{"name":"f",
+		"arkade":{"inputs":[{"name":"sigs","type":"` + typ + `"}],"asm":["<k>","OP_CHECKSIG"]},
+		"leaves":[{"name":"l","witness":[{"name":"s","type":"signature","encoding":"schnorr-64","injected":true}],
+		"asm":["<SERVER_KEY>","OP_CHECKSIGVERIFY","<EMULATOR_KEY:f>","OP_CHECKSIG"]}]}]}`
+	}
+	a, err := ParseArtifact([]byte(doc("bytes[3]")))
+	require.NoError(t, err)
+	require.Equal(t, "bytes[3]", a.Definition.Functions[0].Arkade.Inputs[0].Type)
+	for _, typ := range []string{"float[3]", "bytes[0]", "bytes[]", "bytes[3][2]", "signature[3]"} {
+		_, err := ParseArtifact([]byte(doc(typ)))
+		require.ErrorIs(t, err, ErrInvalidArtifact, typ)
+	}
+}
diff --git a/pkg/template/template.go b/pkg/template/template.go
index 406acbf..d45cb4f 100644
--- a/pkg/template/template.go
+++ b/pkg/template/template.go
@@ -536,6 +536,11 @@ func (p *parser) spend(in *input, v any) error {
 	if f.Arkade != nil {
 		want = f.Arkade.Inputs
 	}
+	for _, w := range want {
+		if arrayType.MatchString(w.Type) {
+			return fmt.Errorf("%w: function %q takes the array input %q, which a template cannot fill", ErrUnsupported, f.Name, w.Name)
+		}
+	}
 	if len(args) != len(want) {
 		return bad("function %q takes %d arguments, got %d", f.Name, len(want), len(args))
 	}
diff --git a/pkg/template/template_test.go b/pkg/template/template_test.go
index 9570489..283aaae 100644
--- a/pkg/template/template_test.go
+++ b/pkg/template/template_test.go
@@ -697,3 +697,27 @@ const vhtlc = `
   "packets": {"output_index": 1, "unmatched": "drop"}
 }
 `
+
+func TestArrayInputs(t *testing.T) {
+	withInput := func(name string) []byte {
+		return edited(t, []byte(releaseDoc), func(m map[string]any) {
+			def := m["inputs"].([]any)[0].(map[string]any)["contract"].(map[string]any)["definition"].(map[string]any)
+			for _, raw := range def["functions"].([]any) {
+				if f := raw.(map[string]any); f["name"] == name {
+					if f["arkade"] == nil {
+						f["arkade"] = map[string]any{"asm": []any{"1"}}
+					}
+					f["arkade"].(map[string]any)["inputs"] = []any{map[string]any{"name": "sigs", "type": "bytes[3]"}}
+					return
+				}
+			}
+			t.Fatalf("releaseDoc has no function %q", name)
+		})
+	}
+	_, err := Parse(t.Context(), withInput("exit"), nil)
+	require.NoError(t, err, "an array input on a function the template does not spend")
+
+	_, err = Parse(t.Context(), withInput("release"), nil)
+	require.ErrorIs(t, err, ErrUnsupported)
+	require.ErrorContains(t, err, `array input "sigs"`)
+}