diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00e89362d231b..5e390575c88d9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -123,7 +123,7 @@ set_property(CACHE SWIFT_ANALYZE_CODE_COVERAGE PROPERTY
 # SWIFT_VERSION is deliberately /not/ cached so that an existing build directory
 # can be reused when a new version of Swift comes out (assuming the user hasn't
 # manually set it as part of their own CMake configuration).
-set(SWIFT_VERSION "5.1.4")
+set(SWIFT_VERSION "5.1.5")
 
 set(SWIFT_VENDOR "" CACHE STRING
     "The vendor name of the Swift compiler")
diff --git a/test/Serialization/Recovery/types-5-to-4.swift b/test/Serialization/Recovery/types-5-to-4.swift
index 0ff64ba5690ad..a800359271641 100644
--- a/test/Serialization/Recovery/types-5-to-4.swift
+++ b/test/Serialization/Recovery/types-5-to-4.swift
@@ -16,8 +16,8 @@ import Lib
 func requiresConformance(_: B_RequiresConformance<B_ConformsToProto>) {}
 func requiresConformance(_: B_RequiresConformance<C_RelyOnConformanceImpl.Assoc>) {}
 
-class Sub: Base {} // expected-error {{cannot inherit from class 'Base' (compiled with Swift 5.1.4) because it has overridable members that could not be loaded in Swift 4.1.50}}
-class Impl: Proto {} // expected-error {{type 'Impl' cannot conform to protocol 'Proto' (compiled with Swift 5.1.4) because it has requirements that could not be loaded in Swift 4.1.50}}
+class Sub: Base {} // expected-error {{cannot inherit from class 'Base' (compiled with Swift 5.1.5) because it has overridable members that could not be loaded in Swift 4.1.50}}
+class Impl: Proto {} // expected-error {{type 'Impl' cannot conform to protocol 'Proto' (compiled with Swift 5.1.5) because it has requirements that could not be loaded in Swift 4.1.50}}
 
 #else // TEST
 
diff --git a/test/SourceKit/Misc/compiler_version.swift b/test/SourceKit/Misc/compiler_version.swift
index 43715d9b99434..e37176423e0ed 100644
--- a/test/SourceKit/Misc/compiler_version.swift
+++ b/test/SourceKit/Misc/compiler_version.swift
@@ -2,4 +2,4 @@
 
 // CHECK: key.version_major: 5
 // CHECK: key.version_minor: 1
-// CHECK: key.version_patch: 4
+// CHECK: key.version_patch: 5
diff --git a/utils/build_swift/defaults.py b/utils/build_swift/defaults.py
index e090e6b08bd39..b59c165b9f3ec 100644
--- a/utils/build_swift/defaults.py
+++ b/utils/build_swift/defaults.py
@@ -40,7 +40,7 @@
 CMAKE_GENERATOR = 'Ninja'
 
 COMPILER_VENDOR = 'none'
-SWIFT_USER_VISIBLE_VERSION = CompilerVersion('5.1.4')
+SWIFT_USER_VISIBLE_VERSION = CompilerVersion('5.1.5')
 CLANG_USER_VISIBLE_VERSION = CompilerVersion('7.0.0')
 SWIFT_ANALYZE_CODE_COVERAGE = 'false'