diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1c70d0375..db4b13588 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,19 @@
 # Change Log
 
+## [1.2.39](https://github.com/ably/ably-cocoa/tree/1.2.39)
+
+### What's Changed
+
+#### Bug fixes
+
+* Fix bug where fallback hosts were not working correctly in custom environments (https://github.com/ably/ably-cocoa/pull/2017)
+
+#### Other changes
+
+* Improvements to the Ably-internal API introduced in v1.2.38 (https://github.com/ably/ably-cocoa/pull/2031)
+
+**Full Changelog**: https://github.com/ably/ably-cocoa/compare/1.2.38...1.2.39
+
 ## [1.2.38](https://github.com/ably/ably-cocoa/tree/1.2.38)
 
 ## What's Changed
diff --git a/README.md b/README.md
index f56be756c..06307fad2 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,7 @@ You can install Ably for iOS and macOS through Package Manager, CocoaPods, Carth
     - [This apple guide](https://developer.apple.com/documentation/swift_packages/adding_package_dependencies_to_your_app) explains the steps in more detail.
 - To install the `ably-cocoa` package in another **Swift Package**, then add the following to your `Package.Swift`:
 ```swift
- .package(url: "https://github.com/ably/ably-cocoa", from: "1.2.38"),
+ .package(url: "https://github.com/ably/ably-cocoa", from: "1.2.39"),
 ```
 ### Installing through [CocoaPods](https://cocoapods.org/)
 
@@ -101,7 +101,7 @@ If you see, for example, a `dyld: Library not loaded: @rpath/AblyDeltaCodec.fram
 
 ### Manual installation 
 
-1. Get the code from GitHub [from the release page](https://github.com/ably/ably-cocoa/releases/tag/1.2.38), or clone it to get the latest, unstable and possibly underdocumented version: `git clone git@github.com:ably/ably-cocoa.git`
+1. Get the code from GitHub [from the release page](https://github.com/ably/ably-cocoa/releases/tag/1.2.39), or clone it to get the latest, unstable and possibly underdocumented version: `git clone git@github.com:ably/ably-cocoa.git`
 2. Drag the directory `ably-cocoa/ably-cocoa` into your project as a group.
 3. Ably depends on our [MessagePack Fork](https://github.com/ably-forks/msgpack-objective-C) 0.2.0; get it [from the releases page](https://github.com/ably-forks/msgpack-objective-C/releases/tag/0.2.0-ably-1) and link it into your project.
 
diff --git a/Scripts/jazzy.sh b/Scripts/jazzy.sh
index a9773cf07..5655ace5b 100755
--- a/Scripts/jazzy.sh
+++ b/Scripts/jazzy.sh
@@ -6,7 +6,7 @@ bundle exec jazzy \
   --objc \
   --clean \
   --author Ably \
-  --module-version 1.2.38 \
+  --module-version 1.2.39 \
   --umbrella-header Source/include/Ably/AblyPublic.h \
   --framework-root Source \
   --module Ably \
diff --git a/Source/ARTClientInformation.m b/Source/ARTClientInformation.m
index 54735234d..28419cc1c 100644
--- a/Source/ARTClientInformation.m
+++ b/Source/ARTClientInformation.m
@@ -6,7 +6,7 @@
 #import <sys/utsname.h>
 
 NSString *const ARTClientInformationAgentNotVersioned = @"ARTClientInformationAgentNotVersioned";
-NSString *const ARTClientInformation_libraryVersion = @"1.2.38";
+NSString *const ARTClientInformation_libraryVersion = @"1.2.39";
 static NSString *const _libraryName = @"ably-cocoa";
 
 // NSOperatingSystemVersion has NSInteger as version components for some reason, so mitigate it here.
diff --git a/Test/Tests/ARTDefaultTests.swift b/Test/Tests/ARTDefaultTests.swift
index 746b55c46..8eed6d9d6 100644
--- a/Test/Tests/ARTDefaultTests.swift
+++ b/Test/Tests/ARTDefaultTests.swift
@@ -6,6 +6,6 @@ class ARTDefaultTests: XCTestCase {
     
     func testVersions() {
         XCTAssertEqual(ARTDefault.apiVersion(), "2")
-        XCTAssertEqual(ARTDefault.libraryVersion(), "1.2.38")
+        XCTAssertEqual(ARTDefault.libraryVersion(), "1.2.39")
     }
 }
diff --git a/Test/Tests/ClientInformationTests.swift b/Test/Tests/ClientInformationTests.swift
index 44a5ea6c5..3e0132c48 100644
--- a/Test/Tests/ClientInformationTests.swift
+++ b/Test/Tests/ClientInformationTests.swift
@@ -9,7 +9,7 @@ final class ClientInformationTests: XCTestCase {
         
         XCTAssertEqual(agents.keys.count, 2)
         
-        XCTAssertEqual(agents["ably-cocoa"], "1.2.38")
+        XCTAssertEqual(agents["ably-cocoa"], "1.2.39")
         
         #if os(iOS)
         XCTAssertTrue(agents.keys.contains("iOS"))
@@ -27,7 +27,7 @@ final class ClientInformationTests: XCTestCase {
     // CR3, CR3b
     func testAgentIdentifierWithAdditionalAgents_withNilAdditionalAgents() {
         let expectedIdentifier = [
-            "ably-cocoa/1.2.38",
+            "ably-cocoa/1.2.39",
             ARTDefault.platformAgent()
         ].sorted().joined(separator: " ")
         
@@ -42,7 +42,7 @@ final class ClientInformationTests: XCTestCase {
         ]
         
         let expectedIdentifier = [
-            "ably-cocoa/1.2.38",
+            "ably-cocoa/1.2.39",
             "demolib/0.0.1",
             "morelib",
             ARTDefault.platformAgent()
diff --git a/Test/Tests/RealtimeClientConnectionTests.swift b/Test/Tests/RealtimeClientConnectionTests.swift
index f362c1fa3..27c6f9350 100644
--- a/Test/Tests/RealtimeClientConnectionTests.swift
+++ b/Test/Tests/RealtimeClientConnectionTests.swift
@@ -384,7 +384,7 @@ class RealtimeClientConnectionTests: XCTestCase {
                     done()
                 case .connected:
                     if let transport = client.internal.transport as? TestProxyTransport, let query = transport.lastUrl?.query {
-                        expect(query).to(haveParam("agent", hasPrefix: "ably-cocoa/1.2.38"))
+                        expect(query).to(haveParam("agent", hasPrefix: "ably-cocoa/1.2.39"))
                     } else {
                         XCTFail("MockTransport isn't working")
                     }
diff --git a/Test/Tests/RestClientTests.swift b/Test/Tests/RestClientTests.swift
index eddfb12c2..c7701d765 100644
--- a/Test/Tests/RestClientTests.swift
+++ b/Test/Tests/RestClientTests.swift
@@ -1736,7 +1736,7 @@ class RestClientTests: XCTestCase {
                 let headerAgent = testHTTPExecutor.requests.first!.allHTTPHeaderFields?["Ably-Agent"]
                 let ablyAgent = ARTClientInformation.agentIdentifier(withAdditionalAgents: options.agents)
                 XCTAssertEqual(headerAgent, ablyAgent)
-                XCTAssertTrue(headerAgent!.hasPrefix("ably-cocoa/1.2.38"))
+                XCTAssertTrue(headerAgent!.hasPrefix("ably-cocoa/1.2.39"))
                 done()
             }
         }
diff --git a/Test/Tests/WrapperSDKProxyTests.swift b/Test/Tests/WrapperSDKProxyTests.swift
index 46dcea79e..e4f94988e 100644
--- a/Test/Tests/WrapperSDKProxyTests.swift
+++ b/Test/Tests/WrapperSDKProxyTests.swift
@@ -220,7 +220,7 @@ class WrapperSDKProxyTests: XCTestCase {
         let request = try XCTUnwrap(testHTTPExecutor.requests.first)
 
         let expectedIdentifier = [
-            "ably-cocoa/1.2.38",
+            "ably-cocoa/1.2.39",
             ARTDefault.platformAgent(),
             "my-wrapper-sdk/1.0.0"
         ].sorted().joined(separator: " ")
@@ -309,7 +309,7 @@ class WrapperSDKProxyTests: XCTestCase {
         XCTAssertEqual(testHTTPExecutor.requests.count, 3) // initial `request()`, `first()`, `next()`
 
         let expectedIdentifier = [
-            "ably-cocoa/1.2.38",
+            "ably-cocoa/1.2.39",
             ARTDefault.platformAgent(),
             "my-wrapper-sdk/1.0.0"
         ].sorted().joined(separator: " ")
@@ -342,7 +342,7 @@ class WrapperSDKProxyTests: XCTestCase {
         XCTAssertEqual(testHTTPExecutor.requests.count, expectedRequestCount)
 
         let expectedIdentifier = [
-            "ably-cocoa/1.2.38",
+            "ably-cocoa/1.2.39",
             ARTDefault.platformAgent(),
             "my-wrapper-sdk/1.0.0"
         ].sorted().joined(separator: " ")
diff --git a/Version.xcconfig b/Version.xcconfig
index 3faf1fee8..c9592d165 100644
--- a/Version.xcconfig
+++ b/Version.xcconfig
@@ -1 +1 @@
-CURRENT_PROJECT_VERSION = 1.2.38
+CURRENT_PROJECT_VERSION = 1.2.39