diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2932920fb..16fdb7420 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,8 @@
 
 #### Breaking
 
-* None.
+* SwiftLint now requires Swift 5.1 or higher to build.  
+  [JP Simard](https://github.com/jpsim)
 
 #### Experimental
 
@@ -10,7 +11,8 @@
 
 #### Enhancements
 
-* JUnit reporter for GitLab artifact:report:junit with better representation of found issues.  
+* JUnit reporter for GitLab artifact:report:junit with better representation of
+  found issues.  
   [krin-san](https://github.com/krin-san)
   [#3177](https://github.com/realm/SwiftLint/pull/3177)
 
diff --git a/Source/SwiftLintFramework/Models/LinterCache.swift b/Source/SwiftLintFramework/Models/LinterCache.swift
index 4f7cde94a..fccfe5b64 100644
--- a/Source/SwiftLintFramework/Models/LinterCache.swift
+++ b/Source/SwiftLintFramework/Models/LinterCache.swift
@@ -18,15 +18,9 @@ private struct FileCache: Codable {
 
 /// A persisted cache for storing and retrieving linter results.
 public final class LinterCache {
-#if canImport(Darwin) || compiler(>=5.1.0)
     private typealias Encoder = PropertyListEncoder
     private typealias Decoder = PropertyListDecoder
     private static let fileExtension = "plist"
-#else
-    private typealias Encoder = JSONEncoder
-    private typealias Decoder = JSONDecoder
-    private static let fileExtension = "json"
-#endif
 
     private typealias Cache = [String: FileCache]
 
diff --git a/Tests/SwiftLintFrameworkTests/CompilerProtocolInitRuleTests.swift b/Tests/SwiftLintFrameworkTests/CompilerProtocolInitRuleTests.swift
index f9f5227f6..9b181ca52 100644
--- a/Tests/SwiftLintFrameworkTests/CompilerProtocolInitRuleTests.swift
+++ b/Tests/SwiftLintFrameworkTests/CompilerProtocolInitRuleTests.swift
@@ -25,7 +25,7 @@ class CompilerProtocolInitRuleTests: XCTestCase {
 }
 
 // https://bugs.swift.org/browse/SR-11501
-#if compiler(<5.1) || (SWIFT_PACKAGE && os(macOS))
+#if SWIFT_PACKAGE && os(macOS) && compiler(<5.2)
 private enum UnwrapError: Error {
     case missingValue
 }
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index c9cf2b500..7a5398757 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -8,8 +8,6 @@ jobs:
   strategy:
     maxParallel: 10
     matrix:
-      swift50:
-        containerImage: swift:5.0
       swift51:
         containerImage: swift:5.1
       # https://bugs.swift.org/browse/SR-12500