diff --git a/expressions/src/completion.ts b/expressions/src/completion.ts
index 1708905..7a29a60 100644
--- a/expressions/src/completion.ts
+++ b/expressions/src/completion.ts
@@ -81,9 +81,6 @@ export function complete(
     extensionFunctions
   );
   const expr = p.parse();
-  if (!expr) {
-    return [];
-  }
 
   const ev = new Evaluator(expr, context, functions);
   const result = ev.evaluate();
diff --git a/expressions/src/evaluator.test.ts b/expressions/src/evaluator.test.ts
index e63ceeb..e1fa8fd 100644
--- a/expressions/src/evaluator.test.ts
+++ b/expressions/src/evaluator.test.ts
@@ -1,14 +1,9 @@
-import {Expr} from "./ast";
 import * as data from "./data";
 import {ExpressionEvaluationError} from "./errors";
 import {Evaluator} from "./evaluator";
 import {Lexer} from "./lexer";
 import {Parser} from "./parser";
 
-function assertDefined(x: Expr | undefined): asserts x is Expr {
-  expect(x).toBeDefined();
-}
-
 describe("evaluator", () => {
   const lexAndParse = (input: string) => {
     const lexer = new Lexer(input);
@@ -17,7 +12,6 @@ describe("evaluator", () => {
     // Parse
     const parser = new Parser(result.tokens, ["foo"], []);
     const expr = parser.parse();
-    assertDefined(expr);
     return expr;
   };
 
diff --git a/expressions/src/parser.ts b/expressions/src/parser.ts
index 9c15c23..6dbb5a2 100644
--- a/expressions/src/parser.ts
+++ b/expressions/src/parser.ts
@@ -43,13 +43,16 @@ export class Parser {
     };
   }
 
-  public parse(): Expr | undefined {
+  public parse(): Expr {
+    // eslint-disable-next-line prefer-const
+    let result!: Expr;
+
     // No tokens
     if (this.atEnd()) {
-      return;
+      return result;
     }
 
-    const result = this.expression();
+    result = this.expression();
 
     if (!this.atEnd()) {
       throw this.buildError(ErrorType.ErrorUnexpectedSymbol, this.peek());
diff --git a/expressions/src/xlang.test.ts b/expressions/src/xlang.test.ts
index 941335b..a7d36be 100644
--- a/expressions/src/xlang.test.ts
+++ b/expressions/src/xlang.test.ts
@@ -119,7 +119,7 @@ describe("x-lang tests", () => {
           // Parse
           const contextNames = testCase.contexts.pairs().map(x => x.key);
           const parser = new Parser(result.tokens, contextNames, []);
-          let expr: Expr | undefined;
+          let expr: Expr;
           try {
             expr = parser.parse();