diff --git a/pkg/parser/parser.go b/pkg/parser/parser.go
index 3ff9390..bc7af89 100644
--- a/pkg/parser/parser.go
+++ b/pkg/parser/parser.go
@@ -72,11 +72,11 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 			args = append(args, arg)
 		}
 
-		close, closeErr := i.Next()
-		if closeErr != nil {
-			return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closeErr)
-		} else if close.Type != tokenizer.TokenCloseParen {
-			return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", close.Value, close.Index)
+		closing, closingErr := i.Next()
+		if closingErr != nil {
+			return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closingErr)
+		} else if closing.Type != tokenizer.TokenCloseParen {
+			return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", closing.Value, closing.Index)
 		}
 
 		// Construction.
diff --git a/pkg/tokenizer/tokenizer.go b/pkg/tokenizer/tokenizer.go
index 9161e57..bdd73f6 100644
--- a/pkg/tokenizer/tokenizer.go
+++ b/pkg/tokenizer/tokenizer.go
@@ -2,11 +2,16 @@ package tokenizer
 
 import (
 	"fmt"
+	"strings"
 	"unicode"
 
 	"git.maximhutz.com/max/lambda/pkg/iterator"
 )
 
+func isVariable(r rune) bool {
+	return unicode.IsLetter(r) || unicode.IsNumber(r)
+}
+
 func getToken(i *iterator.Iterator[rune]) (*Token, error) {
 	if i.IsDone() {
 		return nil, nil
@@ -51,29 +56,25 @@ func getToken(i *iterator.Iterator[rune]) (*Token, error) {
 	}
 
 	// Otherwise, it is an atom.
-	atom := string(letter)
+	atom := strings.Builder{}
 	index := i.Index()
-	for {
-		if i.IsDone() {
-			return &Token{
-				Index: index,
-				Type:  TokenVariable,
-				Value: atom,
-			}, nil
-		}
-
+	for !i.IsDone() {
 		pop, err := i.Peek()
-		if err != nil || unicode.IsSpace(pop) || unicode.IsPunct(pop) {
-			return &Token{
-				Index: index,
-				Type:  TokenVariable,
-				Value: atom,
-			}, nil
+		if err != nil || !isVariable(pop) {
+			break
 		}
 
-		i.Next()
-		atom += string(pop)
+		atom.WriteRune(pop)
+		if _, err := i.Next(); err != nil {
+			break
+		}
 	}
+
+	return &Token{
+		Index: index,
+		Type:  TokenVariable,
+		Value: atom.String(),
+	}, nil
 }
 
 func GetTokens(input []rune) ([]Token, []error) {