diff --git a/src/builtin/tags/assign.ts b/src/builtin/tags/assign.ts
index 9902f1f62a..8891105137 100644
--- a/src/builtin/tags/assign.ts
+++ b/src/builtin/tags/assign.ts
@@ -1,4 +1,4 @@
-import { Tokenizer, assert, TagImplOptions, TagToken, Context } from '../../types'
+import { Value, Tokenizer, assert, TagImplOptions, TagToken, Context } from '../../types'
 
 export default {
   parse: function (token: TagToken) {
@@ -7,9 +7,9 @@ export default {
     tokenizer.skipBlank()
     assert(tokenizer.peek() === '=', () => `illegal token ${token.getText()}`)
     tokenizer.advance()
-    this.value = tokenizer.remaining()
+    this.value = new Value(tokenizer.remaining(), this.liquid)
   },
   render: function * (ctx: Context): Generator<unknown, void, unknown> {
-    ctx.bottom()[this.key] = yield this.liquid._evalValue(this.value, ctx)
+    ctx.bottom()[this.key] = yield this.value.value(ctx, this.liquid.options.lenientIf)
   }
 } as TagImplOptions
diff --git a/test/e2e/issues.ts b/test/e2e/issues.ts
index 72570be4f1..f81a7be792 100644
--- a/test/e2e/issues.ts
+++ b/test/e2e/issues.ts
@@ -256,4 +256,8 @@ describe('Issues', function () {
     const html = engine.parseAndRenderSync(`{% for i in (1..10000) %}{{ i }}{% endfor %}`)
     expect(html).to.have.lengthOf(38894)
   })
+  it('#519 should throw parse error for invalid assign expression', () => {
+    const engine = new Liquid()
+    expect(() => engine.parse('{% assign headshot = https://testurl.com/not_enclosed_in_quotes.jpg %}')).to.throw(/unexpected token at ":/)
+  })
 })
diff --git a/test/integration/builtin/tags/assign.ts b/test/integration/builtin/tags/assign.ts
index 5f08b99991..201562a42d 100644
--- a/test/integration/builtin/tags/assign.ts
+++ b/test/integration/builtin/tags/assign.ts
@@ -1,4 +1,4 @@
-import { Liquid } from '../../../../src/liquid'
+import { ParseError, Liquid } from '../../../../src/liquid'
 import { expect, use } from 'chai'
 import * as chaiAsPromised from 'chai-as-promised'
 
@@ -16,9 +16,10 @@ describe('tags/assign', function () {
     const html = await liquid.parseAndRender(src)
     return expect(html).to.equal('bar')
   })
-  it('should throw when variable value illegal', async function () {
+  it('should throw when variable value illegal', function () {
     const src = '{% assign foo = “bar” %}'
-    return expect(liquid.parseAndRender(src)).to.be.rejectedWith(/unexpected token at "“bar”"/)
+    expect(() => liquid.parse(src)).to.throw(/unexpected token at "“bar”"/)
+    expect(() => liquid.parse(src)).to.throw(ParseError)
   })
   it('should support assign to a number', async function () {
     const src = '{% assign foo=10086 %}{{foo}}'