diff --git a/package-lock.json b/package-lock.json
index 59edf5a86b..5a5574e1f4 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,6 +5,7 @@
   "requires": true,
   "packages": {
     "": {
+      "name": "assemblyscript",
       "version": "0.0.0",
       "license": "Apache-2.0",
       "dependencies": {
diff --git a/src/compiler.ts b/src/compiler.ts
index 0ee4365ecb..c01ef852cc 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -474,7 +474,7 @@ export class Compiler extends DiagnosticEmitter {
     module.setFeatures(featureFlags);
 
     // set up the main start function
-    let startFunctionInstance = program.makeNativeFunction(BuiltinNames.start, new Signature(program, [], Type.void));
+    let startFunctionInstance = program.makeNativeFunction(BuiltinNames.start, Signature.create(program, [], Type.void));
     startFunctionInstance.internalName = BuiltinNames.start;
     this.currentFlow = startFunctionInstance.flow;
     this.currentBody = new Array<ExpressionRef>();
@@ -6430,8 +6430,8 @@ export class Compiler extends DiagnosticEmitter {
     assert(operandIndex == minOperands);
 
     // create the varargs stub
-    stub = original.newStub("varargs");
-    stub.signature.requiredParameters = maxArguments;
+    stub = original.newStub("varargs", maxArguments);
+
     original.varargsStub = stub;
 
     // compile initializers of omitted arguments in the scope of the stub,
@@ -7102,8 +7102,7 @@ export class Compiler extends DiagnosticEmitter {
         }
       }
 
-      let signature = new Signature(this.program, parameterTypes, returnType, thisType);
-      signature.requiredParameters = numParameters; // !
+      let signature = Signature.create(this.program, parameterTypes, returnType, thisType, numParameters);
       instance = new Function(
         prototype.name,
         prototype,
@@ -8669,7 +8668,7 @@ export class Compiler extends DiagnosticEmitter {
             )
           ),
           null,
-          new Signature(this.program, null, classInstance.type, classInstance.type),
+          Signature.create(this.program, [], classInstance.type, classInstance.type),
           contextualTypeArguments
         );
       }
diff --git a/src/program.ts b/src/program.ts
index 63360df1be..abfcfe6162 100644
--- a/src/program.ts
+++ b/src/program.ts
@@ -472,7 +472,7 @@ export class Program extends DiagnosticEmitter {
   /** Managed classes contained in the program, by id. */
   managedClasses: Map<i32,Class> = new Map();
   /** A set of unique function signatures contained in the program, by id. */
-  uniqueSignatures: Signature[] = new Array<Signature>(0);
+  uniqueSignatures: Map<string, Signature> = new Map<string, Signature>();
   /** Module exports. */
   moduleExports: Map<string,Element> = new Map();
   /** Module imports. */
@@ -3217,7 +3217,7 @@ export class File extends Element {
     program.filesByName.set(this.internalName, this);
     let startFunction = this.program.makeNativeFunction(
       `start:${this.internalName}`,
-      new Signature(program, null, Type.void),
+      Signature.create(program, [], Type.void),
       this
     );
     startFunction.internalName = startFunction.name;
@@ -3826,12 +3826,12 @@ export class Function extends TypedElement {
   }
 
   /** Creates a stub for use with this function, i.e. for varargs or override calls. */
-  newStub(postfix: string): Function {
+  newStub(postfix: string, requiredParameters: i32 = this.signature.requiredParameters): Function {
     let stub = new Function(
       this.original.name + STUB_DELIMITER + postfix,
       this.prototype,
       this.typeArguments,
-      this.signature.clone(),
+      this.signature.clone(requiredParameters),
       this.contextualTypeArguments
     );
     stub.original = this.original;
diff --git a/src/resolver.ts b/src/resolver.ts
index f9baff992d..20005b954d 100644
--- a/src/resolver.ts
+++ b/src/resolver.ts
@@ -422,9 +422,7 @@ export class Resolver extends DiagnosticEmitter {
       );
       if (!returnType) return null;
     }
-    let signature = new Signature(this.program, parameterTypes, returnType, thisType);
-    signature.requiredParameters = requiredParameters;
-    signature.hasRest = hasRest;
+    let signature = Signature.create(this.program, parameterTypes, returnType, thisType, requiredParameters, hasRest);
     return node.isNullable ? signature.type.asNullable() : signature.type;
   }
 
@@ -2706,7 +2704,14 @@ export class Resolver extends DiagnosticEmitter {
       }
       const type = this.resolveExpression(expr, tempFlow, ctxType, reportMode);
       if (type) {
-        signatureReference.returnType = type;
+        functionType.signatureReference = Signature.create(
+          this.program,
+          signatureReference.parameterTypes,
+          type,
+          signatureReference.thisType,
+          signatureReference.requiredParameters,
+          signatureReference.hasRest,
+        );
       }
     }
     return functionType;
@@ -2853,8 +2858,7 @@ export class Resolver extends DiagnosticEmitter {
       returnType = type;
     }
 
-    let signature = new Signature(this.program, parameterTypes, returnType, thisType);
-    signature.requiredParameters = requiredParameters;
+    let signature = Signature.create(this.program, parameterTypes, returnType, thisType, requiredParameters);
 
     let nameInclTypeParameters = prototype.name;
     if (instanceKey.length) nameInclTypeParameters += `<${instanceKey}>`;
diff --git a/src/types.ts b/src/types.ts
index a0074edc70..baad2a89f5 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -421,12 +421,17 @@ export class Type {
 
   /** Tests if this type equals the specified. */
   equals(other: Type): bool {
-    if (this.kind != other.kind) return false;
+    if (this.kind != other.kind) {
+      return false;
+    }
     if (this.isReference) {
+      let selfSignatureReference = this.signatureReference;
+      let otherSignatureReference = other.signatureReference;
+
       return (
-        this.classReference == other.classReference &&
-        this.signatureReference == other.signatureReference &&
-        this.isNullableReference == other.isNullableReference
+        this.classReference == other.classReference
+        && selfSignatureReference == otherSignatureReference
+        && this.isNullableReference == other.isNullableReference
       );
     }
     return true;
@@ -882,58 +887,71 @@ export function typesToString(types: Type[]): string {
 
 /** Represents a fully resolved function signature. */
 export class Signature {
-  /** Unique id representing this signature. */
-  id: u32 = 0;
-  /** Parameter types, if any, excluding `this`. */
-  parameterTypes: Type[];
-  /** Number of required parameters excluding `this`. Other parameters are considered optional. */
-  requiredParameters: i32;
-  /** Return type. */
-  returnType: Type;
-  /** This type, if an instance signature. */
-  thisType: Type | null;
-  /** Whether the last parameter is a rest parameter. */
-  hasRest: bool;
-  /** Respective function type. */
-  type: Type;
-  /** The program that created this signature. */
-  program: Program;
-
-  /** Constructs a new signature. */
-  constructor(
+  /** Construct a new signature. */
+  public static create(
+    /** The program that created this signature. */
     program: Program,
-    parameterTypes: Type[] | null = null,
-    returnType: Type | null = null,
-    thisType: Type | null = null
-  ) {
-    this.parameterTypes = parameterTypes ? parameterTypes : [];
-    this.requiredParameters = 0;
-    this.returnType = returnType ? returnType : Type.void;
-    this.thisType = thisType;
-    this.program = program;
-    this.hasRest = false;
+    /** Parameter types, if any, excluding `this`. */
+    parameterTypes: Type[] = [],
+    /** Return type. */
+    returnType: Type = Type.void,
+    /** This type, if an instance signature. */
+    thisType: Type | null = null,
+    /** Number of required parameters excluding `this`. Other parameters are considered optional. */
+    requiredParameters: i32 = parameterTypes ? parameterTypes.length : 0,
+    /** Whether the last parameter is a rest parameter. */
+    hasRest: bool = false,
+  ): Signature {
+    // get the usize type, and the type of the signature
     let usizeType = program.options.usizeType;
     let type = new Type(
       usizeType.kind,
       usizeType.flags & ~TypeFlags.Value | TypeFlags.Reference,
       usizeType.size
     );
-    this.type = type;
-    type.signatureReference = this;
 
+    // calculate the properties
     let signatureTypes = program.uniqueSignatures;
-    let length = signatureTypes.length;
-    for (let i = 0; i < length; i++) {
-      let compare = unchecked(signatureTypes[i]);
-      if (this.equals(compare)) {
-        this.id = compare.id;
-        return this;
-      }
+    let nextId = program.nextSignatureId;
+    
+    // construct the signature and calculate it's unique key
+    let signature = new Signature(program, parameterTypes, returnType, thisType, requiredParameters, hasRest, nextId, type);
+    let uniqueKey = signature.toString();
+
+    // check if it exists, and return it
+    if (signatureTypes.has(uniqueKey)) {
+      let existing = assert(signatureTypes.get(uniqueKey));
+      assert(signature.equals(existing));
+      return existing;
     }
-    this.id = program.nextSignatureId++;
-    signatureTypes.push(this);
+
+    // otherwise increment the program's signature id, set the signature reference of the type, and memoize the signature
+    program.nextSignatureId = nextId + 1;
+    type.signatureReference = signature;
+    signatureTypes.set(uniqueKey, signature);
+    return signature;
   }
 
+  /** Constructs a new signature. */
+  private constructor(
+    /** The program that created this signature. */
+    public readonly program: Program,
+    /** Parameter types, if any, excluding `this`. */
+    public readonly parameterTypes: Type[],
+    /** Return type. */
+    public readonly returnType: Type,
+    /** This type, if an instance signature. */
+    public readonly thisType: Type | null,
+    /** Number of required parameters excluding `this`. Other parameters are considered optional. */
+    public readonly requiredParameters: i32,
+    /** Whether the last parameter is a rest parameter. */
+    public readonly hasRest: bool,
+    /** Unique id representing this signature. */
+    public readonly id: u32,
+    /** Respective function type. */
+    public readonly type: Type,
+  ) {}
+
   get paramRefs(): TypeRef {
     let thisType = this.thisType;
     let parameterTypes = this.parameterTypes;
@@ -975,15 +993,15 @@ export class Signature {
     if (!this.returnType.equals(other.returnType)) return false;
 
     // check parameter types
-    let thisParameterTypes = this.parameterTypes;
+    let selfParameterTypes = this.parameterTypes;
     let otherParameterTypes = other.parameterTypes;
-    let numParameters = thisParameterTypes.length;
-    if (numParameters != otherParameterTypes.length) return false;
+    let numParameters = selfParameterTypes.length;
+    if (numParameters != otherParameterTypes.length)  return false;
 
     for (let i = 0; i < numParameters; ++i) {
-      let thisParameterType = unchecked(thisParameterTypes[i]);
+      let selfParameterType = unchecked(selfParameterTypes[i]);
       let otherParameterType = unchecked(otherParameterTypes[i]);
-      if (!thisParameterType.equals(otherParameterType)) return false;
+      if (!selfParameterType.equals(otherParameterType)) return false;
     }
     return true;
   }
@@ -1105,7 +1123,6 @@ export class Signature {
     let thisType = this.thisType;
     if (thisType) {
       sb.push(validWat ? "this:" : "this: ");
-      assert(!thisType.signatureReference);
       sb.push(thisType.toString(validWat));
       index = 1;
     }
@@ -1127,18 +1144,20 @@ export class Signature {
   }
 
   /** Creates a clone of this signature that is safe to modify. */
-  clone(): Signature {
+  clone(requiredParameters: i32 = this.requiredParameters, hasRest: bool = this.hasRest): Signature {
     let parameterTypes = this.parameterTypes;
     let numParameterTypes = parameterTypes.length;
     let cloneParameterTypes = new Array<Type>(numParameterTypes);
     for (let i = 0; i < numParameterTypes; ++i) {
       unchecked(cloneParameterTypes[i] = parameterTypes[i]);
     }
-    return new Signature(
+    return Signature.create(
       this.program,
       cloneParameterTypes,
       this.returnType,
-      this.thisType
+      this.thisType,
+      requiredParameters,
+      hasRest
     );
   }
 }
diff --git a/tests/compiler/builtins.debug.wat b/tests/compiler/builtins.debug.wat
index 9986eafa4e..22e152bde3 100644
--- a/tests/compiler/builtins.debug.wat
+++ b/tests/compiler/builtins.debug.wat
@@ -3213,11 +3213,11 @@
   local.set $48
   i32.const 0
   local.set $49
-  i32.const 46
+  i32.const 51
   local.set $50
-  i32.const 47
+  i32.const 52
   local.set $51
-  i32.const 47
+  i32.const 52
   local.set $52
   i32.const 256
   local.set $63
@@ -3262,7 +3262,7 @@
    unreachable
   end
   local.get $50
-  i32.const 46
+  i32.const 51
   i32.eq
   i32.eqz
   if
diff --git a/tests/compiler/builtins.release.wat b/tests/compiler/builtins.release.wat
index de997e4994..7ef85acda2 100644
--- a/tests/compiler/builtins.release.wat
+++ b/tests/compiler/builtins.release.wat
@@ -735,9 +735,9 @@
   i32.const 5
   f64.const 0
   f64.const 0
-  f64.const 46
-  f64.const 47
-  f64.const 47
+  f64.const 51
+  f64.const 52
+  f64.const 52
   call $~lib/builtins/trace
   global.get $~lib/memory/__stack_pointer
   local.tee $0