diff --git a/src/liquid-options.ts b/src/liquid-options.ts
index d6f9f893a3..2e14e4d7f5 100644
--- a/src/liquid-options.ts
+++ b/src/liquid-options.ts
@@ -1,4 +1,3 @@
-import { deprecate } from './util/deprecate'
 import * as _ from './util/underscore'
 
 export interface LiquidOptions {
@@ -77,13 +76,6 @@ export function normalize (options?: LiquidOptions): NormalizedOptions {
   if (options.hasOwnProperty('root')) {
     options.root = normalizeStringArray(options.root)
   }
-  for (const key of Object.keys(options)) {
-    if (key.indexOf('_') > -1) {
-      const newKey = key.replace(/_([a-z])/g, (_, ch) => ch.toUpperCase())
-      deprecate(`${key} is deprecated, use ${newKey} instead.`, 109)
-      options[newKey] = options[key]
-    }
-  }
   return options as NormalizedOptions
 }
 
diff --git a/src/scope/context.ts b/src/scope/context.ts
index 7789e0ad42..71fd188795 100644
--- a/src/scope/context.ts
+++ b/src/scope/context.ts
@@ -2,9 +2,7 @@ import { Drop } from '../drop/drop'
 
 type PlainObject = {
   [key: string]: any
-  liquid_method_missing?: (key: string) => any // eslint-disable-line
-  to_liquid?: () => any // eslint-disable-line
-  toLiquid?: () => any  // eslint-disable-line
+  toLiquid?: () => any
 }
 
-export type Context = PlainObject | Drop
\ No newline at end of file
+export type Context = PlainObject | Drop
diff --git a/src/scope/scope.ts b/src/scope/scope.ts
index 1c00f31426..ae251b6782 100644
--- a/src/scope/scope.ts
+++ b/src/scope/scope.ts
@@ -22,7 +22,7 @@ export default class Scope {
   async get (path: string) {
     const paths = await this.propertyAccessSeq(path)
     let ctx = this.findContextFor(paths[0]) || _.last(this.contexts)
-    for (let path of paths) {
+    for (const path of paths) {
       ctx = this.readProperty(ctx, path)
       if (_.isNil(ctx) && this.opts.strictVariables) {
         throw new TypeError(`undefined variable: ${path}`)
diff --git a/src/template/filter/filter.ts b/src/template/filter/filter.ts
index e931415c81..af4c20d968 100644
--- a/src/template/filter/filter.ts
+++ b/src/template/filter/filter.ts
@@ -21,7 +21,7 @@ export class Filter {
   }
   async render (value: any, scope: Scope) {
     const argv: any[] = []
-    for(let arg of this.args) {
+    for (const arg of this.args) {
       if (isArray(arg)) argv.push([arg[0], await evalValue(arg[1], scope)])
       else argv.push(await evalValue(arg, scope))
     }
diff --git a/src/template/value.ts b/src/template/value.ts
index 23418136d7..35b653405d 100644
--- a/src/template/value.ts
+++ b/src/template/value.ts
@@ -49,7 +49,7 @@ export default class Value {
   }
   async value (scope: Scope) {
     let val = await evalExp(this.initial, scope)
-    for (let filter of this.filters) {
+    for (const filter of this.filters) {
       val = await filter.render(val, scope)
     }
     return val
diff --git a/src/util/deprecate.ts b/src/util/deprecate.ts
deleted file mode 100644
index 9e4a5baa3d..0000000000
--- a/src/util/deprecate.ts
+++ /dev/null
@@ -1,7 +0,0 @@
-const reported:{[key: string]: boolean} = {}
-
-export function deprecate (msg: string, issue: number) {
-  if (reported[msg]) return
-  console.warn(msg + ` See: https://github.com/harttle/liquidjs/issues/${issue}`)
-  reported[msg] = true
-}
diff --git a/src/util/underscore.ts b/src/util/underscore.ts
index 057bab6672..7de9c1c63c 100644
--- a/src/util/underscore.ts
+++ b/src/util/underscore.ts
@@ -1,4 +1,3 @@
-import { deprecate } from './deprecate'
 const toStr = Object.prototype.toString
 
 /*
@@ -29,18 +28,10 @@ export function promisify (fn: any) {
 export function stringify (value: any): string {
   if (isNil(value)) return ''
   value = toLiquid(value)
-  if (isFunction(value.to_s)) {
-    deprecate('to_s is deprecated, use toString instead.', 109)
-    return value.to_s()
-  }
   return String(value)
 }
 
 export function toLiquid (value: any): any {
-  if (isFunction(value.to_liquid)) {
-    deprecate('to_liquid is deprecated, use toLiquid instead.', 109)
-    return toLiquid(value.to_liquid())
-  }
   if (isFunction(value.toLiquid)) return toLiquid(value.toLiquid())
   return value
 }
diff --git a/test/integration/liquid/strict.ts b/test/integration/liquid/strict.ts
index c813675f3a..09c2b9d8c5 100644
--- a/test/integration/liquid/strict.ts
+++ b/test/integration/liquid/strict.ts
@@ -1,7 +1,7 @@
 import Liquid from '../../../src/liquid'
 import { expect } from 'chai'
 
-describe('LiquidOptions#strict_*', function () {
+describe('LiquidOptions#strict*', function () {
   let engine: Liquid
   const ctx = {}
   beforeEach(function () {
diff --git a/test/integration/liquid/trimming.ts b/test/integration/liquid/trimming.ts
index 63c8b16a22..dc99715671 100644
--- a/test/integration/liquid/trimming.ts
+++ b/test/integration/liquid/trimming.ts
@@ -5,35 +5,35 @@ describe('LiquidOptions#trimming', function () {
   const ctx = { name: 'harttle' }
 
   describe('tag trimming', function () {
-    it('should respect trim_tag_left', async function () {
-      const engine = new Liquid({ trim_tag_left: true } as any)
+    it('should respect trimTagLeft', async function () {
+      const engine = new Liquid({ trimTagLeft: true })
       const html = await engine.parseAndRender(' \n \t{%if true%}foo{%endif%} ')
       return expect(html).to.equal('foo ')
     })
-    it('should respect trim_tag_right', async function () {
-      const engine = new Liquid({ trim_tag_right: true } as any)
+    it('should respect trimTagRight', async function () {
+      const engine = new Liquid({ trimTagRight: true } as any)
       const html = await engine.parseAndRender('\t{%if true%}foo{%endif%} \n')
       return expect(html).to.equal('\tfoo')
     })
     it('should not trim value', async function () {
-      const engine = new Liquid({ trim_tag_left: true, trim_tag_right: true } as any)
+      const engine = new Liquid({ trimTagLeft: true, trimTagRight: true } as any)
       const html = await engine.parseAndRender('{%if true%}a {{name}} b{%endif%}', ctx)
       return expect(html).to.equal('a harttle b')
     })
   })
   describe('value trimming', function () {
-    it('should respect trim_output_left', async function () {
-      const engine = new Liquid({ trim_output_left: true } as any)
+    it('should respect trimOutputLeft', async function () {
+      const engine = new Liquid({ trimOutputLeft: true } as any)
       const html = await engine.parseAndRender(' \n \t{{name}} ', ctx)
       return expect(html).to.equal('harttle ')
     })
-    it('should respect trim_output_right', async function () {
-      const engine = new Liquid({ trim_output_right: true } as any)
+    it('should respect trimOutputRight', async function () {
+      const engine = new Liquid({ trimOutputRight: true } as any)
       const html = await engine.parseAndRender(' \n \t{{name}} ', ctx)
       return expect(html).to.equal(' \n \tharttle')
     })
     it('should respect not trim tag', async function () {
-      const engine = new Liquid({ trim_output_left: true, trim_output_right: true } as any)
+      const engine = new Liquid({ trimOutputLeft: true, trimOutputRight: true } as any)
       const html = await engine.parseAndRender('\t{% if true %} aha {%endif%}\t')
       return expect(html).to.equal('\t aha \t')
     })
diff --git a/test/unit/scope/scope.ts b/test/unit/scope/scope.ts
index 70cc2ee2d9..8563fae087 100644
--- a/test/unit/scope/scope.ts
+++ b/test/unit/scope/scope.ts
@@ -85,15 +85,6 @@ describe('scope', function () {
     it("should throw when '' unbalanced", async function () {
       expect(scope.get("foo['bar]")).to.be.rejectedWith(/unbalanced '/)
     })
-
-    it('should respect to to_liquid', async function () {
-      const scope = new Scope({ foo: {
-        to_liquid: () => ({ bar: 'BAR' }),
-        bar: 'bar'
-      } })
-      expect(await scope.get('foo.bar')).to.equal('BAR')
-    })
-
     it('should respect to toLiquid', async function () {
       const scope = new Scope({ foo: {
         toLiquid: () => ({ bar: 'BAR' }),
diff --git a/test/unit/template/output.ts b/test/unit/template/output.ts
index 5f2900841e..b4dad3c28b 100644
--- a/test/unit/template/output.ts
+++ b/test/unit/template/output.ts
@@ -11,14 +11,6 @@ describe('Output', function () {
     Filter.clear()
   })
 
-  it('should respect to .to_liquid() method', async function () {
-    const scope = new Scope({
-      bar: { to_liquid: () => 'custom' }
-    })
-    const output = new Output({ value: 'bar' } as OutputToken, false)
-    const html = await output.render(scope)
-    return expect(html).to.equal('custom')
-  })
   it('should stringify objects', async function () {
     const scope = new Scope({
       foo: { obj: { arr: ['a', 2] } }
@@ -39,12 +31,6 @@ describe('Output', function () {
     const str = await output.render(scope)
     return expect(str).to.equal('FOO')
   })
-  it('should respect to .to_s()', async () => {
-    const scope = new Scope({ obj: { to_s: () => 'FOO' } })
-    const output = new Output({ value: 'obj' } as OutputToken, false)
-    const str = await output.render(scope)
-    return expect(str).to.equal('FOO')
-  })
   it('should respect to .toString()', async () => {
     const scope = new Scope({ obj: { toString: () => 'FOO' } })
     const output = new Output({ value: 'obj' } as OutputToken, false)
diff --git a/test/unit/util/underscore.ts b/test/unit/util/underscore.ts
index 814862ff03..269fca031f 100644
--- a/test/unit/util/underscore.ts
+++ b/test/unit/util/underscore.ts
@@ -19,9 +19,6 @@ describe('util/underscore', function () {
     })
   })
   describe('.stringify()', function () {
-    it('should respect to to_liquid() method', function () {
-      expect(_.stringify({ to_liquid: () => 'foo' })).to.equal('foo')
-    })
     it('should respect to toLiquid() method', function () {
       expect(_.stringify({ toLiquid: () => 'foo' })).to.equal('foo')
     })