diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d1c4521..b2731da 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,20 +35,28 @@ jobs:
     strategy:
       matrix:
         swift:
+          - 5.3
           - 5.4
           - 5.5
     steps:
       - uses: actions/checkout@v2
       - name: Run tests
-        run: make test-linux-${{ matrix.swift }}
+        run: make test-linux SWIFT_VERSION=${{ matrix.swift }}
 
   windows:
     name: Windows
     runs-on: windows-latest
+    strategy:
+      matrix:
+        swift:
+          #- 5.3
+          - 5.4
+          - 5.5
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v2
       - name: Install Swift & Run tests
         uses: MaxDesiatov/swift-windows-action@v1
         with:
-          shell-action: swift test && swift build -c release
+          shell-action: swift test && swift build --configuration release
+          swift-version: ${{ matrix.swift }}
diff --git a/Makefile b/Makefile
index 4d9d11c..9e10a23 100644
--- a/Makefile
+++ b/Makefile
@@ -3,29 +3,25 @@ PLATFORM_MACOS = macOS
 PLATFORM_MAC_CATALYST = macOS,variant=Mac Catalyst
 PLATFORM_TVOS = tvOS Simulator,name=Apple TV 4K (at 1080p)
 PLATFORM_WATCHOS = watchOS Simulator,name=Apple Watch Series 4 - 44mm
+SWIFT_VERSION = 5.5
+ifeq ($(SWIFT_VERSION),5.3)
+SWIFT_BUILD_ARGS = --enable-test-discovery
+endif
+SWIFT_TEST_ARGS = --parallel
 
-test-all: test-linux-all test-swift test-platforms
+test-all: test-linux test-swift test-platforms
 
-test-linux-all: test-linux-5.4 test-linux-5.5
-
-test-linux-5.4:
-	$(call test-linux,5.4)
-
-test-linux-5.5:
-	$(call test-linux,5.5)
-
-test-linux = docker run \
-	--rm \
-	-v "$(PWD):$(PWD)" \
-	-w "$(PWD)" \
-	swift:$(1) \
-	bash -c 'make test-swift'
+test-linux:
+	docker run \
+		--rm \
+		-v "$(PWD):$(PWD)" \
+		-w "$(PWD)" \
+		swift:$(SWIFT_VERSION) \
+		bash -c 'make test-swift SWIFT_VERSION=$(SWIFT_VERSION)'
 
 test-swift:
-	swift test \
-		--parallel
-	swift build \
-		--configuration release
+	swift test $(SWIFT_BUILD_ARGS) $(SWIFT_TEST_ARGS)
+	swift build --configuration release $(SWIFT_BUILD_ARGS)
 
 test-platforms:
 	xcodebuild test \
diff --git a/Sources/CustomDump/Conformances/Foundation.swift b/Sources/CustomDump/Conformances/Foundation.swift
index 2d0a8b3..861ba66 100644
--- a/Sources/CustomDump/Conformances/Foundation.swift
+++ b/Sources/CustomDump/Conformances/Foundation.swift
@@ -5,8 +5,8 @@ import Foundation
 #endif
 
 // NB: Xcode 13 does not include macOS 12 SDK
-// NB: Swift 5.5 does not include AttributedString in Linux (yet)
-#if compiler(>=5.5) && !os(macOS) && !targetEnvironment(macCatalyst) && !os(Linux)
+// NB: Swift 5.5 does not include AttributedString on other platforms (yet)
+#if compiler(>=5.5) && !targetEnvironment(macCatalyst) && (os(iOS) || os(tvOS) || os(watchOS))
   @available(iOS 15, macOS 12, tvOS 15, watchOS 8, *)
   extension AttributedString: CustomDumpRepresentable {
     public var customDumpValue: Any {
diff --git a/Tests/CustomDumpTests/DumpTests.swift b/Tests/CustomDumpTests/DumpTests.swift
index 0bc62da..f7155d2 100644
--- a/Tests/CustomDumpTests/DumpTests.swift
+++ b/Tests/CustomDumpTests/DumpTests.swift
@@ -718,7 +718,7 @@ final class DumpTests: XCTestCase {
   func testFoundation() {
     var dump = ""
 
-    #if compiler(>=5.5) && !os(macOS) && !targetEnvironment(macCatalyst) && !os(Linux)
+    #if compiler(>=5.5) && !targetEnvironment(macCatalyst) && (os(iOS) || os(tvOS) || os(watchOS))
       if #available(iOS 15, macOS 12, tvOS 15, watchOS 8, *) {
         dump = ""
         customDump(
@@ -967,7 +967,7 @@ final class DumpTests: XCTestCase {
         DumpTests.(unknown context).(unknown context).BridgedError.thisIsFine(94)
         """
       )
-    #else
+    #elseif compiler(>=5.4)
       // Can't unwrap bridged Errors on Linux: https://bugs.swift.org/browse/SR-15191
       XCTAssertNoDifference(
         dump.replacingOccurrences(