diff --git a/Sources/Nimble/Adapters/NMBExpectation.swift b/Sources/Nimble/Adapters/NMBExpectation.swift
index 4279c7780..6ca25fb7b 100644
--- a/Sources/Nimble/Adapters/NMBExpectation.swift
+++ b/Sources/Nimble/Adapters/NMBExpectation.swift
@@ -14,7 +14,7 @@ private func from(objcMatcher: NMBMatcher) -> Matcher<NSObject> {
 
 // Equivalent to Expectation, but for Nimble's Objective-C interface
 public final class NMBExpectation: NSObject, Sendable {
-    internal let _actualBlock: @Sendable () -> NSObject?
+    internal let _actualBlock: @Sendable () -> sending NSObject?
     internal let _negative: Bool
     internal let _file: FileString
     internal let _line: UInt
diff --git a/Sources/Nimble/Matchers/AllPass.swift b/Sources/Nimble/Matchers/AllPass.swift
index f1f6e2b5d..489f2e4bb 100644
--- a/Sources/Nimble/Matchers/AllPass.swift
+++ b/Sources/Nimble/Matchers/AllPass.swift
@@ -100,7 +100,9 @@ extension NMBMatcher {
                 )
             }
 
-            let expr = Expression(expression: ({ nsObjects }), location: location)
+            let immutableCollection = nsObjects
+
+            let expr = Expression(expression: ({ immutableCollection }), location: location)
             let pred: Matcher<[NSObject]> = createMatcher(Matcher { expr in
                 return matcher.satisfies(({ try expr.evaluate() }), location: expr.location).toSwift()
             })
diff --git a/Sources/Nimble/Matchers/BeCloseTo.swift b/Sources/Nimble/Matchers/BeCloseTo.swift
index 36dc0e00f..0031d8f3e 100644
--- a/Sources/Nimble/Matchers/BeCloseTo.swift
+++ b/Sources/Nimble/Matchers/BeCloseTo.swift
@@ -67,7 +67,7 @@ private func beCloseTo(
 }
 
 #if canImport(Darwin)
-public class NMBObjCBeCloseToMatcher: NMBMatcher {
+public final class NMBObjCBeCloseToMatcher: NMBMatcher, @unchecked Sendable {
     private let _expected: NSNumber
 
     fileprivate init(expected: NSNumber, within: CDouble) {
diff --git a/Sources/Nimble/Matchers/BeEmpty.swift b/Sources/Nimble/Matchers/BeEmpty.swift
index 43e1ca791..cdec3e606 100644
--- a/Sources/Nimble/Matchers/BeEmpty.swift
+++ b/Sources/Nimble/Matchers/BeEmpty.swift
@@ -88,7 +88,8 @@ extension NMBMatcher {
                 let expr = Expression(expression: { value }, location: location)
                 return try beEmpty().satisfies(expr).toObjectiveC()
             } else if let value = actualValue as? NSString {
-                let expr = Expression(expression: { value }, location: location)
+                let stringValue = String(value)
+                let expr = Expression(expression: { stringValue }, location: location)
                 return try beEmpty().satisfies(expr).toObjectiveC()
             } else if let actualValue = actualValue {
                 let badTypeErrorMsg = "be empty (only works for NSArrays, NSSets, NSIndexSets, NSDictionaries, NSHashTables, and NSStrings)"
diff --git a/Sources/Nimble/Matchers/Contain.swift b/Sources/Nimble/Matchers/Contain.swift
index 555d4d1ff..93e5364f9 100644
--- a/Sources/Nimble/Matchers/Contain.swift
+++ b/Sources/Nimble/Matchers/Contain.swift
@@ -77,10 +77,14 @@ public func contain(_ substrings: NSString...) -> Matcher<NSString> {
 }
 
 public func contain(_ substrings: [NSString]) -> Matcher<NSString> {
+    let stringSubstrings = substrings.map { String($0) }
     return Matcher.simple("contain <\(arrayAsString(substrings))>") { actualExpression in
         guard let actual = try actualExpression.evaluate() else { return .fail }
+        let actualString = String(actual)
 
-        let matches = substrings.allSatisfy { actual.range(of: $0.description).length != 0 }
+        let matches = stringSubstrings.allSatisfy { string in
+            actualString.contains(string)
+        }
         return MatcherStatus(bool: matches)
     }
 }
@@ -115,7 +119,8 @@ extension NMBMatcher {
                 let expectedOptionals: [Any?] = expected.map({ $0 as Any? })
                 return try contain(expectedOptionals).satisfies(expr).toObjectiveC()
             } else if let value = actualValue as? NSString {
-                let expr = Expression(expression: ({ value as String }), location: location)
+                let stringValue = String(value)
+                let expr = Expression(expression: ({ stringValue }), location: location)
                 // swiftlint:disable:next force_cast
                 return try contain(expected as! [String]).satisfies(expr).toObjectiveC()
             }
diff --git a/Sources/Nimble/Matchers/Matcher.swift b/Sources/Nimble/Matchers/Matcher.swift
index ffb5798b5..470985f60 100644
--- a/Sources/Nimble/Matchers/Matcher.swift
+++ b/Sources/Nimble/Matchers/Matcher.swift
@@ -225,7 +225,7 @@ public class NMBMatcher: NSObject, @unchecked Sendable {
         self.init(matcher: predicate)
     }
 
-    func satisfies(_ expression: @escaping @Sendable () throws -> NSObject?, location: SourceLocation) -> NMBMatcherResult {
+    func satisfies(_ expression: @escaping @Sendable () throws -> sending NSObject?, location: SourceLocation) -> NMBMatcherResult {
         let expr = Expression(expression: expression, location: location)
         do {
             return try self.matcher(expr)
diff --git a/Tests/NimbleTests/Matchers/BeAKindOfTest.swift b/Tests/NimbleTests/Matchers/BeAKindOfTest.swift
index 93bf7b9fa..1160eb57a 100644
--- a/Tests/NimbleTests/Matchers/BeAKindOfTest.swift
+++ b/Tests/NimbleTests/Matchers/BeAKindOfTest.swift
@@ -5,9 +5,9 @@ import Nimble
 import NimbleSharedTestHelpers
 #endif
 
-private class TestNull: NSNull {}
+private final class TestNull: NSNull, @unchecked Sendable {}
 private protocol TestProtocol {}
-private class TestClassConformingToProtocol: TestProtocol {}
+private final class TestClassConformingToProtocol: TestProtocol {}
 private struct TestStructConformingToProtocol: TestProtocol {}
 
 final class BeAKindOfSwiftTest: XCTestCase {