diff --git a/src/option/none.ts b/src/option/none.ts
index 415bff7..18e5f4c 100644
--- a/src/option/none.ts
+++ b/src/option/none.ts
@@ -47,7 +47,7 @@ class None_<A> implements Option<A> {
     throw new Option.NoSuchElementError();
   }
 
-  getOrElse<B, A extends B>(this: None_<A>, defaultValue: () => B): B {
+  getOrElse<B, A extends B>(this: Option<A>, defaultValue: () => B): B {
     return defaultValue();
   }
 
@@ -59,7 +59,7 @@ class None_<A> implements Option<A> {
     return matcher.None();
   }
 
-  orElse<B, A extends B>(this: None_<A>, alternative: () => Option<B>): Option<B> {
+  orElse<B, A extends B>(this: Option<A>, alternative: () => Option<B>): Option<B> {
     return alternative();
   }
 }
diff --git a/src/option/some.ts b/src/option/some.ts
index 67b8c88..7b5180b 100644
--- a/src/option/some.ts
+++ b/src/option/some.ts
@@ -53,8 +53,10 @@ class Some<A> implements Option<A> {
     return this.value;
   }
 
-  getOrElse<B, A extends B>(this: Some<A>, defaultValue: () => B): B {
-    return this.value;
+  getOrElse<B, A extends B>(this: Option<A>, defaultValue: () => B): B {
+    const self: Some<A> = this as Some<A>;
+
+    return self.value;
   }
 
   map<B>(mapper: (value: A) => B): Option<B> {
@@ -65,8 +67,10 @@ class Some<A> implements Option<A> {
     return matcher.Some(this.value);
   }
 
-  orElse<B, A extends B>(this: Some<A>, alternative: () => Option<B>): Option<B> {
-    return this;
+  orElse<B, A extends B>(this: Option<A>, alternative: () => Option<B>): Option<B> {
+    const self: Some<A> = this as Some<A>;
+
+    return self;
   }
 }
 
diff --git a/src/try/failure.ts b/src/try/failure.ts
index 39937aa..da5e78d 100644
--- a/src/try/failure.ts
+++ b/src/try/failure.ts
@@ -45,7 +45,7 @@ class Failure<A> implements Try<A> {
     throw this.error;
   }
 
-  getOrElse<B, A extends B>(this: Failure<A>, defaultValue: () => B): B {
+  getOrElse<B, A extends B>(this: Try<A>, defaultValue: () => B): B {
     return defaultValue();
   }
 
@@ -57,7 +57,7 @@ class Failure<A> implements Try<A> {
     return matcher.Failure(this.error);
   }
 
-  orElse<B, A extends B>(this: Failure<A>, alternative: () => Try<B>): Try<B> {
+  orElse<B, A extends B>(this: Try<A>, alternative: () => Try<B>): Try<B> {
     return alternative();
   }
 
diff --git a/src/try/success.ts b/src/try/success.ts
index 68b91e1..95dd3c2 100644
--- a/src/try/success.ts
+++ b/src/try/success.ts
@@ -46,8 +46,10 @@ class Success<A> implements Try<A> {
     return this.value;
   }
 
-  getOrElse<B, A extends B>(this: Success<A>, defaultValue: () => B): B {
-    return this.value;
+  getOrElse<B, A extends B>(this: Try<A>, defaultValue: () => B): B {
+    const self: Success<A> = this as Success<A>;
+
+    return self.value;
   }
 
   map<B>(f: (value: A) => B): Try<B> {
@@ -58,8 +60,10 @@ class Success<A> implements Try<A> {
     return matcher.Success(this.value);
   }
 
-  orElse<B, A extends B>(this: Success<A>, alternative: () => Try<B>): Try<B> {
-    return this;
+  orElse<B, A extends B>(this: Try<A>, alternative: () => Try<B>): Try<B> {
+    const self: Success<A> = this as Success<A>;
+
+    return self;
   }
 
   recover(fn: (error: Error) => A): Try<A> {