diff --git a/cmd/bench/main.go b/cmd/bench/main.go
index e275608..17a8093 100644
--- a/cmd/bench/main.go
+++ b/cmd/bench/main.go
@@ -193,7 +193,7 @@ func compileFile(file *ast.File) (time.Duration, *compiler.Bytecode, error) {
 
 	start := time.Now()
 
-	c := compiler.NewCompiler(symTable, nil)
+	c := compiler.NewCompiler(symTable, nil, nil)
 	if err := c.Compile(file); err != nil {
 		return time.Since(start), nil, err
 	}
diff --git a/cmd/tengo/main.go b/cmd/tengo/main.go
index 777321c..5ebb054 100644
--- a/cmd/tengo/main.go
+++ b/cmd/tengo/main.go
@@ -171,7 +171,11 @@ func doRepl(in io.Reader, out io.Writer) {
 
 	fileSet := source.NewFileSet()
 	globals := make([]*objects.Object, runtime.GlobalsSize)
+
 	symbolTable := compiler.NewSymbolTable()
+	for idx, fn := range objects.Builtins {
+		symbolTable.DefineBuiltin(idx, fn.Name)
+	}
 
 	for {
 		_, _ = fmt.Fprintf(out, replPrompt)
@@ -191,7 +195,7 @@ func doRepl(in io.Reader, out io.Writer) {
 
 		file = addPrints(file)
 
-		c := compiler.NewCompiler(symbolTable, nil)
+		c := compiler.NewCompiler(symbolTable, nil, nil)
 		if err := c.Compile(file); err != nil {
 			_, _ = fmt.Fprintf(out, "Compilation error:\n %s\n", err.Error())
 			continue
@@ -218,7 +222,7 @@ func compileSrc(src []byte, filename string) (*compiler.Bytecode, error) {
 		return nil, err
 	}
 
-	c := compiler.NewCompiler(nil, nil)
+	c := compiler.NewCompiler(nil, nil, nil)
 	if err := c.Compile(file); err != nil {
 		return nil, err
 	}
diff --git a/compiler/compiler.go b/compiler/compiler.go
index ba5a26b..1b3b331 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -20,6 +20,7 @@ type Compiler struct {
 	scopes          []CompilationScope
 	scopeIndex      int
 	moduleLoader    ModuleLoader
+	stdModules      map[string]*objects.ImmutableMap
 	compiledModules map[string]*objects.CompiledModule
 	loops           []*Loop
 	loopIndex       int
@@ -28,17 +29,28 @@ type Compiler struct {
 }
 
 // NewCompiler creates a Compiler.
-func NewCompiler(symbolTable *SymbolTable, trace io.Writer) *Compiler {
+// User can optionally provide the symbol table if one wants to add or remove
+// some global- or builtin- scope symbols. If not (nil), Compile will create
+// a new symbol table and use the default builtin functions. Likewise, standard
+// modules can be explicitly provided if user wants to add or remove some modules.
+// By default, Compile will use all the standard modules otherwise.
+func NewCompiler(symbolTable *SymbolTable, stdModules map[string]*objects.ImmutableMap, trace io.Writer) *Compiler {
 	mainScope := CompilationScope{
 		instructions: make([]byte, 0),
 	}
 
+	// symbol table
 	if symbolTable == nil {
 		symbolTable = NewSymbolTable()
+
+		for idx, fn := range objects.Builtins {
+			symbolTable.DefineBuiltin(idx, fn.Name)
+		}
 	}
 
-	for idx, fn := range objects.Builtins {
-		symbolTable.DefineBuiltin(idx, fn.Name)
+	// standard modules
+	if stdModules == nil {
+		stdModules = stdlib.Modules
 	}
 
 	return &Compiler{
@@ -47,6 +59,7 @@ func NewCompiler(symbolTable *SymbolTable, trace io.Writer) *Compiler {
 		scopeIndex:      0,
 		loopIndex:       -1,
 		trace:           trace,
+		stdModules:      stdModules,
 		compiledModules: make(map[string]*objects.CompiledModule),
 	}
 }
@@ -440,7 +453,7 @@ func (c *Compiler) Compile(node ast.Node) error {
 		c.emit(OpCall, len(node.Args))
 
 	case *ast.ImportExpr:
-		stdMod, ok := stdlib.Modules[node.ModuleName]
+		stdMod, ok := c.stdModules[node.ModuleName]
 		if ok {
 			// standard modules contain only globals with no code.
 			// so no need to compile anything
@@ -474,12 +487,14 @@ func (c *Compiler) Bytecode() *Bytecode {
 }
 
 // SetModuleLoader sets or replaces the current module loader.
+// Note that the module loader is used for user modules,
+// not for the standard modules.
 func (c *Compiler) SetModuleLoader(moduleLoader ModuleLoader) {
 	c.moduleLoader = moduleLoader
 }
 
 func (c *Compiler) fork(moduleName string, symbolTable *SymbolTable) *Compiler {
-	child := NewCompiler(symbolTable, c.trace)
+	child := NewCompiler(symbolTable, c.stdModules, c.trace)
 	child.moduleName = moduleName       // name of the module to compile
 	child.parent = c                    // parent to set to current compiler
 	child.moduleLoader = c.moduleLoader // share module loader
diff --git a/compiler/compiler_test.go b/compiler/compiler_test.go
index c63b053..5dfefe5 100644
--- a/compiler/compiler_test.go
+++ b/compiler/compiler_test.go
@@ -972,9 +972,12 @@ func traceCompile(input string, symbols map[string]objects.Object) (res *compile
 	for name := range symbols {
 		symTable.Define(name)
 	}
+	for idx, fn := range objects.Builtins {
+		symTable.DefineBuiltin(idx, fn.Name)
+	}
 
 	tr := &tracer{}
-	c := compiler.NewCompiler(symTable, tr)
+	c := compiler.NewCompiler(symTable, nil, tr)
 	parsed, err := p.ParseFile()
 	if err != nil {
 		return
diff --git a/objects/builtins.go b/objects/builtins.go
index acf2419..fe7085e 100644
--- a/objects/builtins.go
+++ b/objects/builtins.go
@@ -1,10 +1,13 @@
 package objects
 
-// Builtins contains all known builtin functions.
-var Builtins = []struct {
+// NamedBuiltinFunc is a named builtin function.
+type NamedBuiltinFunc struct {
 	Name string
 	Func CallableFunc
-}{
+}
+
+// Builtins contains all default builtin functions.
+var Builtins = []NamedBuiltinFunc{
 	{
 		Name: "print",
 		Func: builtinPrint,
diff --git a/runtime/vm_test.go b/runtime/vm_test.go
index d14eaef..f3f0722 100644
--- a/runtime/vm_test.go
+++ b/runtime/vm_test.go
@@ -176,9 +176,12 @@ func traceCompileRun(file *ast.File, symbols map[string]objects.Object, userModu
 		sym := symTable.Define(name)
 		globals[sym.Index] = &value
 	}
+	for idx, fn := range objects.Builtins {
+		symTable.DefineBuiltin(idx, fn.Name)
+	}
 
 	tr := &tracer{}
-	c := compiler.NewCompiler(symTable, tr)
+	c := compiler.NewCompiler(symTable, nil, tr)
 	c.SetModuleLoader(func(moduleName string) ([]byte, error) {
 		if src, ok := userModules[moduleName]; ok {
 			return []byte(src), nil
diff --git a/script/script.go b/script/script.go
index 32933eb..418b3f3 100644
--- a/script/script.go
+++ b/script/script.go
@@ -63,7 +63,7 @@ func (s *Script) Compile() (*Compiled, error) {
 		return nil, fmt.Errorf("parse error: %s", err.Error())
 	}
 
-	c := compiler.NewCompiler(symbolTable, nil)
+	c := compiler.NewCompiler(symbolTable, nil, nil)
 	if err := c.Compile(file); err != nil {
 		return nil, err
 	}
@@ -94,6 +94,10 @@ func (s *Script) prepCompile() (symbolTable *compiler.SymbolTable, globals []*ob
 	}
 
 	symbolTable = compiler.NewSymbolTable()
+	for idx, fn := range objects.Builtins {
+		symbolTable.DefineBuiltin(idx, fn.Name)
+	}
+
 	globals = make([]*objects.Object, len(names), len(names))
 
 	for idx, name := range names {