diff --git a/ast/ast.go b/ast/ast.go
index 1e9f389..4154914 100644
--- a/ast/ast.go
+++ b/ast/ast.go
@@ -444,6 +444,9 @@ const (
 	ObjectFieldExpr                        // '['expr1']':[:[:]] expr2
 	ObjectFieldStr                         // expr1:[:[:]] expr2
 	ObjectLocal                            // local id = expr2
+	ObjectNullID                           // null id
+	ObjectNullExpr                         // null '['expr1']'
+	ObjectNullStr                          // null expr1
 )
 
 type ObjectFieldHide int
diff --git a/interpreter.go b/interpreter.go
index 3e95116..cc7238c 100644
--- a/interpreter.go
+++ b/interpreter.go
@@ -942,22 +942,20 @@ func evaluateAux(i *interpreter, node ast.Node, tla vmExtMap) (value, *TraceElem
 	if err != nil {
 		return nil, nil, err
 	}
-	if len(tla) != 0 {
-		// If it's not a function, ignore TLA
-		if f, ok := result.(*valueFunction); ok {
-			toplevelArgMap := prepareExtVars(i, tla, "top-level-arg")
-			args := callArguments{}
-			for argName, pv := range toplevelArgMap {
-				args.named = append(args.named, namedCallArgument{name: ast.Identifier(argName), pv: pv})
-			}
-			funcLoc := ast.MakeLocationRangeMessage("Top-level function")
-			funcTrace := &TraceElement{
-				loc: &funcLoc,
-			}
-			result, err = f.call(args).getValue(i, funcTrace)
-			if err != nil {
-				return nil, nil, err
-			}
+	// If it's not a function, ignore TLA
+	if f, ok := result.(*valueFunction); ok {
+		toplevelArgMap := prepareExtVars(i, tla, "top-level-arg")
+		args := callArguments{}
+		for argName, pv := range toplevelArgMap {
+			args.named = append(args.named, namedCallArgument{name: ast.Identifier(argName), pv: pv})
+		}
+		funcLoc := ast.MakeLocationRangeMessage("Top-level function")
+		funcTrace := &TraceElement{
+			loc: &funcLoc,
+		}
+		result, err = f.call(args).getValue(i, funcTrace)
+		if err != nil {
+			return nil, nil, err
 		}
 	}
 	manifestationLoc := ast.MakeLocationRangeMessage("During manifestation")
diff --git a/testdata/function.golden b/testdata/function_manifested.golden
similarity index 100%
rename from testdata/function.golden
rename to testdata/function_manifested.golden
diff --git a/testdata/function_manifested.jsonnet b/testdata/function_manifested.jsonnet
new file mode 100644
index 0000000..265a376
--- /dev/null
+++ b/testdata/function_manifested.jsonnet
@@ -0,0 +1,3 @@
+{
+    f(x): 3,
+}
diff --git a/testdata/function_no_params.golden b/testdata/function_no_params.golden
new file mode 100644
index 0000000..d81cc07
--- /dev/null
+++ b/testdata/function_no_params.golden
@@ -0,0 +1 @@
+42
diff --git a/testdata/function.jsonnet b/testdata/function_no_params.jsonnet
similarity index 100%
rename from testdata/function.jsonnet
rename to testdata/function_no_params.jsonnet
diff --git a/testdata/function_too_many_params.golden b/testdata/function_too_many_params.golden
new file mode 100644
index 0000000..273e011
--- /dev/null
+++ b/testdata/function_too_many_params.golden
@@ -0,0 +1,5 @@
+RUNTIME ERROR: Missing argument: x
+-------------------------------------------------
+	Top-level function	
+
+
diff --git a/testdata/function_too_many_params.jsonnet b/testdata/function_too_many_params.jsonnet
new file mode 100644
index 0000000..1285c2e
--- /dev/null
+++ b/testdata/function_too_many_params.jsonnet
@@ -0,0 +1 @@
+function(x) 3