diff --git a/Sources/AssertThat/AssertThat.swift b/Sources/AssertThat/AssertThat.swift
index 7ea6ec7..bdf71bb 100644
--- a/Sources/AssertThat/AssertThat.swift
+++ b/Sources/AssertThat/AssertThat.swift
@@ -1,3 +1,3 @@
-public func assertThat<T>(_ expression: @escaping @autoclosure () throws -> T) -> Assertion<T> {
-    Assertion(expression: expression)
+public func assertThat<Subject>(_ subject: Subject) -> Assertion<Subject> {
+    Assertion(subject: subject)
 }
diff --git a/Sources/AssertThat/Assertion.swift b/Sources/AssertThat/Assertion.swift
index 2ab4871..61ca2d6 100644
--- a/Sources/AssertThat/Assertion.swift
+++ b/Sources/AssertThat/Assertion.swift
@@ -1,7 +1,3 @@
 public struct Assertion<Subject> {
-    public let expression: () throws -> Subject
-
-    public var subject: Subject {
-        try! expression() // swiftlint:disable:this force_try
-    }
+    public let subject: Subject
 }
diff --git a/Sources/AssertThat/Extensions/Closure.swift b/Sources/AssertThat/Extensions/Closure.swift
index 1eb9f26..a27b9c0 100644
--- a/Sources/AssertThat/Extensions/Closure.swift
+++ b/Sources/AssertThat/Extensions/Closure.swift
@@ -4,7 +4,7 @@ public extension Assertion where Subject == () throws -> Any {
     @discardableResult
     func throwsAnError(file: StaticString = #filePath, line: UInt = #line) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
             XCTFail("no error was thrown", file: file, line: line)
         } catch {}
         return self
@@ -13,7 +13,7 @@ public extension Assertion where Subject == () throws -> Any {
     @discardableResult
     func doesNotThrowAnError(file: StaticString = #filePath, line: UInt = #line) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
         } catch {
             XCTFail("\(error) was thrown", file: file, line: line)
         }
@@ -27,7 +27,7 @@ public extension Assertion where Subject == () throws -> Any {
         line: UInt = #line
     ) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
             XCTFail("\(expectedError) was not thrown", file: file, line: line)
         } catch {
             XCTAssertTrue(error as? T == expectedError, "\(error) is not \(expectedError)", file: file, line: line)
@@ -42,7 +42,7 @@ public extension Assertion where Subject == () throws -> Any {
         line: UInt = #line
     ) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
         } catch {
             XCTAssertFalse(error as? T == expectedError, "\(expectedError) was thrown", file: file, line: line)
         }
@@ -52,7 +52,7 @@ public extension Assertion where Subject == () throws -> Any {
     @discardableResult
     func `throws`<T: Error>(_ expectedError: T.Type, file: StaticString = #filePath, line: UInt = #line) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
             XCTFail("\(expectedError) was not thrown", file: file, line: line)
         } catch {
             XCTAssertTrue(type(of: error) == T.self, "\(error) is not \(expectedError)", file: file, line: line)
@@ -63,7 +63,7 @@ public extension Assertion where Subject == () throws -> Any {
     @discardableResult
     func doesNotThrow<T: Error>(_ expectedError: T.Type, file: StaticString = #filePath, line: UInt = #line) -> Self {
         do {
-            _ = try expression()()
+            _ = try subject()
         } catch {
             XCTAssertFalse(type(of: error) == T.self, "\(expectedError) was thrown", file: file, line: line)
         }