diff --git a/src/build/Function.go b/src/build/Function.go
index 4bd2a94..7a2b103 100644
--- a/src/build/Function.go
+++ b/src/build/Function.go
@@ -74,8 +74,6 @@ func (f *Function) CompileTokens(body token.List) error {
 				if err != nil {
 					return err
 				}
-
-				start = -1
 			}
 
 			start = i + 1
diff --git a/src/build/compile.go b/src/build/compile.go
index 325bcd5..c028a68 100644
--- a/src/build/compile.go
+++ b/src/build/compile.go
@@ -51,30 +51,11 @@ func compile(functions <-chan *Function, errors <-chan error) (Result, error) {
 
 	result.Used = append(result.Used, main)
 	delete(result.Unused, "main")
-	result.findCalls(main)
+	result.findAliveCode(main)
 
 	return result, nil
 }
 
-func (result *Result) findCalls(f *Function) {
-	for _, x := range f.Assembler.Instructions {
-		if x.Mnemonic != asm.CALL {
-			continue
-		}
-
-		name := x.Data.(*asm.Label).Name
-		called, exists := result.Unused[name]
-
-		if !exists {
-			continue
-		}
-
-		result.Used = append(result.Used, called)
-		delete(result.Unused, name)
-		result.findCalls(called)
-	}
-}
-
 // compileFunctions starts a goroutine for each function compilation and waits for completion.
 func compileFunctions(functions map[string]*Function) {
 	wg := sync.WaitGroup{}
@@ -90,3 +71,23 @@ func compileFunctions(functions map[string]*Function) {
 
 	wg.Wait()
 }
+
+// findAliveCode recursively finds all the calls to external functions and marks them as required.
+func (result *Result) findAliveCode(f *Function) {
+	for _, x := range f.Assembler.Instructions {
+		if x.Mnemonic != asm.CALL {
+			continue
+		}
+
+		name := x.Data.(*asm.Label).Name
+		called, exists := result.Unused[name]
+
+		if !exists {
+			continue
+		}
+
+		result.Used = append(result.Used, called)
+		delete(result.Unused, name)
+		result.findAliveCode(called)
+	}
+}
diff --git a/src/build/expression/Expression_test.go b/src/build/expression/Expression_test.go
index c0fe259..e267a60 100644
--- a/src/build/expression/Expression_test.go
+++ b/src/build/expression/Expression_test.go
@@ -102,14 +102,15 @@ func TestEachLeaf(t *testing.T) {
 	expr := expression.Parse(tokens)
 	leaves := []string{}
 
-	expr.EachLeaf(func(leaf *expression.Expression) error {
+	err := expr.EachLeaf(func(leaf *expression.Expression) error {
 		leaves = append(leaves, leaf.Token.Text())
 		return nil
 	})
 
+	assert.Nil(t, err)
 	assert.DeepEqual(t, leaves, []string{"1", "2", "3", "4", "5", "6", "7", "8"})
 
-	err := expr.EachLeaf(func(leaf *expression.Expression) error {
+	err = expr.EachLeaf(func(leaf *expression.Expression) error {
 		return fmt.Errorf("error")
 	})
 
diff --git a/src/build/expression/List.go b/src/build/expression/List.go
index 2bb4b56..75c44d0 100644
--- a/src/build/expression/List.go
+++ b/src/build/expression/List.go
@@ -4,8 +4,8 @@ import (
 	"git.akyoto.dev/cli/q/src/build/token"
 )
 
-// List generates a list of expressions from comma separated parameters.
-func List(tokens token.List) []*Expression {
+// NewList generates a list of expressions from comma separated parameters.
+func NewList(tokens token.List) []*Expression {
 	var list []*Expression
 
 	EachParameter(tokens, func(parameter token.List) error {
diff --git a/src/build/expression/Parse.go b/src/build/expression/Parse.go
index 536718b..072dfe4 100644
--- a/src/build/expression/Parse.go
+++ b/src/build/expression/Parse.go
@@ -38,7 +38,7 @@ func Parse(tokens token.List) *Expression {
 			isFunctionCall := isComplete(cursor)
 
 			if isFunctionCall {
-				parameters := List(tokens[groupPosition:i])
+				parameters := NewList(tokens[groupPosition:i])
 
 				node := New()
 				node.Token.Kind = token.Operator
diff --git a/src/build/fs/Walk_test.go b/src/build/fs/Walk_test.go
index ae55b3d..d3f6e17 100644
--- a/src/build/fs/Walk_test.go
+++ b/src/build/fs/Walk_test.go
@@ -10,10 +10,11 @@ import (
 func TestWalk(t *testing.T) {
 	var files []string
 
-	fs.Walk(".", func(file string) {
+	err := fs.Walk(".", func(file string) {
 		files = append(files, file)
 	})
 
+	assert.Nil(t, err)
 	assert.Contains(t, files, "Walk.go")
 	assert.Contains(t, files, "Walk_test.go")
 }