diff --git a/compiler/forget/src/Babel/PluginOptions.ts b/compiler/forget/src/Babel/PluginOptions.ts
index 0e47a59cfb..eaaf90015c 100644
--- a/compiler/forget/src/Babel/PluginOptions.ts
+++ b/compiler/forget/src/Babel/PluginOptions.ts
@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import { EnvironmentOptions } from "../HIR/Environment";
+import { EnvironmentConfig } from "../HIR/Environment";
 
 export type PluginOptions = {
   /**
@@ -13,7 +13,7 @@ export type PluginOptions = {
    */
   enableOnlyOnUseForgetDirective: boolean;
 
-  environment: Partial<EnvironmentOptions> | null;
+  environment: EnvironmentConfig | null;
 
   logger: Logger | null;
 
diff --git a/compiler/forget/src/CompilerPipeline.ts b/compiler/forget/src/CompilerPipeline.ts
index e628207fc2..80fb6dc299 100644
--- a/compiler/forget/src/CompilerPipeline.ts
+++ b/compiler/forget/src/CompilerPipeline.ts
@@ -12,7 +12,7 @@ import {
   mergeConsecutiveBlocks,
   ReactiveFunction,
 } from "./HIR";
-import { EnvironmentOptions, mergeOptions } from "./HIR/Environment";
+import { EnvironmentConfig, Environment } from "./HIR/Environment";
 import { validateConsistentIdentifiers } from "./HIR/ValidateConsistentIdentifiers";
 import {
   analyseFunctions,
@@ -51,9 +51,9 @@ export type CompilerPipelineValue =
 
 export function* run(
   func: NodePath<t.FunctionDeclaration>,
-  options?: Partial<EnvironmentOptions> | null
+  config?: EnvironmentConfig | null
 ): Generator<CompilerPipelineValue, t.FunctionDeclaration> {
-  const hir = lower(func, mergeOptions(options ?? null)).unwrap();
+  const hir = lower(func, new Environment(config ?? null)).unwrap();
   yield log({ kind: "hir", name: "HIR", value: hir });
 
   mergeConsecutiveBlocks(hir);
@@ -147,7 +147,7 @@ export function* run(
   });
 
   pruneNonEscapingScopes(reactiveFunction, {
-    memoizeJsxElements: options?.memoizeJsxElements ?? true,
+    memoizeJsxElements: config?.memoizeJsxElements ?? true,
   });
   yield log({
     kind: "reactive",
@@ -205,7 +205,7 @@ export function* run(
 
 export function compile(
   func: NodePath<t.FunctionDeclaration>,
-  options?: Partial<EnvironmentOptions> | null
+  options?: Partial<EnvironmentConfig> | null
 ): t.FunctionDeclaration {
   let generator = run(func, options);
   while (true) {
diff --git a/compiler/forget/src/HIR/BuildHIR.ts b/compiler/forget/src/HIR/BuildHIR.ts
index 0cb6f316ac..9aaa6ce52f 100644
--- a/compiler/forget/src/HIR/BuildHIR.ts
+++ b/compiler/forget/src/HIR/BuildHIR.ts
@@ -12,7 +12,7 @@ import invariant from "invariant";
 import { CompilerError, ErrorSeverity } from "../CompilerError";
 import { Err, Ok, Result } from "../Utils/Result";
 import { assertExhaustive } from "../Utils/utils";
-import { Environment, EnvironmentOptions } from "./Environment";
+import { Environment } from "./Environment";
 import {
   ArrayPattern,
   BlockId,
@@ -57,13 +57,11 @@ import HIRBuilder from "./HIRBuilder";
  */
 export function lower(
   func: NodePath<t.Function>,
-  options: EnvironmentOptions | null,
+  env: Environment,
   capturedRefs: t.Identifier[] = [],
   // the outermost function being compiled, in case lower() is called recursively (for lambdas)
-  parent: NodePath<t.Function> | null = null,
-  environment: Environment | null = null
+  parent: NodePath<t.Function> | null = null
 ): Result<HIRFunction, CompilerError> {
-  const env = environment ?? new Environment(options);
   const builder = new HIRBuilder(env, parent ?? func, capturedRefs);
   const context: Place[] = [];
 
@@ -2013,10 +2011,9 @@ function lowerFunctionExpression(
   // identify the correct references.
   const lowering = lower(
     expr,
-    builder.environment.options,
+    builder.environment,
     [...builder.context, ...captured.identifiers],
-    builder.parentFunction,
-    builder.environment
+    builder.parentFunction
   );
   let loweredFunc: HIRFunction;
   if (lowering.isErr()) {
diff --git a/compiler/forget/src/HIR/Environment.ts b/compiler/forget/src/HIR/Environment.ts
index d41e044713..28aa5abfaa 100644
--- a/compiler/forget/src/HIR/Environment.ts
+++ b/compiler/forget/src/HIR/Environment.ts
@@ -11,41 +11,29 @@ import {
   ValueKind,
 } from "./HIR";
 import { BUILTIN_HOOKS, Hook } from "./Hooks";
-import { BUILTIN_SHAPES, FunctionSignature } from "./ObjectShape";
+import {
+  BUILTIN_SHAPES,
+  FunctionSignature,
+  ShapeRegistry,
+} from "./ObjectShape";
 
 const HOOK_PATTERN = /^_?use/;
 
-export type EnvironmentOptions = {
+export type EnvironmentConfig = Partial<{
   customHooks: Map<string, Hook>;
-  globals: Set<string>;
   memoizeJsxElements: boolean;
-};
-
-const DEFAULT_OPTIONS: EnvironmentOptions = {
-  customHooks: new Map(),
-  globals: DEFAULT_GLOBALS,
-  memoizeJsxElements: true,
-};
-
-export function mergeOptions(
-  options: Partial<EnvironmentOptions> | null
-): EnvironmentOptions {
-  return {
-    ...DEFAULT_OPTIONS,
-    ...(options ?? {}),
-  };
-}
+}>;
 
 export class Environment {
-  #options: EnvironmentOptions;
+  #customHooks: Map<string, Hook>;
+  #globals: Set<string>;
+  #shapes: ShapeRegistry;
   #nextIdentifer: number = 0;
 
-  constructor(options: EnvironmentOptions | null) {
-    this.#options = options ?? DEFAULT_OPTIONS;
-  }
-
-  get options(): EnvironmentOptions {
-    return this.#options;
+  constructor(config: EnvironmentConfig | null) {
+    this.#customHooks = config?.customHooks ?? new Map();
+    this.#shapes = BUILTIN_SHAPES;
+    this.#globals = DEFAULT_GLOBALS;
   }
 
   get nextIdentifierId(): IdentifierId {
@@ -53,7 +41,7 @@ export class Environment {
   }
 
   getGlobalDeclaration(name: string): Global | null {
-    if (!this.#options.globals.has(name)) {
+    if (!this.#globals.has(name)) {
       log(() => `Undefined global '${name}'`);
     }
     return { name };
@@ -63,7 +51,7 @@ export class Environment {
     if (!name.match(HOOK_PATTERN)) {
       return null;
     }
-    const hook = BUILTIN_HOOKS.get(name) ?? this.#options.customHooks.get(name);
+    const hook = BUILTIN_HOOKS.get(name) ?? this.#customHooks.get(name);
     if (hook !== undefined) {
       return hook;
     }
@@ -83,7 +71,7 @@ export class Environment {
     if (shapeId !== null) {
       // If an object or function has a shapeId, it must have been assigned
       // by Forget (and be present in a builtin or user-defined registry)
-      const shape = BUILTIN_SHAPES.get(shapeId);
+      const shape = this.#shapes.get(shapeId);
       invariant(
         shape !== undefined,
         `[HIR] Forget internal error: cannot resolve shape ${shapeId}`
@@ -97,7 +85,7 @@ export class Environment {
   getFunctionSignature(type: FunctionType): FunctionSignature | null {
     const { shapeId } = type;
     if (shapeId !== null) {
-      const shape = BUILTIN_SHAPES.get(shapeId);
+      const shape = this.#shapes.get(shapeId);
       invariant(
         shape !== undefined,
         `[HIR] Forget internal error: cannot resolve shape ${shapeId}`
diff --git a/compiler/forget/src/__tests__/hir-test.ts b/compiler/forget/src/__tests__/hir-test.ts
index ef5fc5457f..b828be1e8b 100644
--- a/compiler/forget/src/__tests__/hir-test.ts
+++ b/compiler/forget/src/__tests__/hir-test.ts
@@ -7,19 +7,19 @@
 
 "use strict";
 
-import * as t from "@babel/types";
 import { parse } from "@babel/parser";
 import traverse, { NodePath } from "@babel/traverse";
+import * as t from "@babel/types";
 import path from "path";
 
+import invariant from "invariant";
 import * as CompilerPipeline from "../CompilerPipeline";
 import { Effect, ValueKind } from "../HIR";
+import { EnvironmentConfig } from "../HIR/Environment";
 import { printFunction } from "../HIR/PrintHIR";
-import { EnvironmentOptions } from "../HIR/Environment";
-import { Result, Ok, Err } from "../Utils/Result";
 import { toggleLogging } from "../Utils/logger";
+import { Err, Ok, Result } from "../Utils/Result";
 import generateTestsFromFixtures from "./test-utils/generateTestsFromFixtures";
-import invariant from "invariant";
 
 // TODO: make pipeline names an enum
 // Currently, this is the last pass that operates on hir
@@ -81,7 +81,7 @@ type CompileResult = {
 function compile(
   source: string,
   language: "flow" | "typescript",
-  compilerEnv: Partial<EnvironmentOptions>
+  compilerEnv: Partial<EnvironmentConfig>
 ): Result<Array<CompileResult>, Error> {
   const transformedFns = new Array<CompileResult>();
   const babelAsts = parseFunctions(source, language);