diff --git a/Package.swift b/Package.swift
index 251b5acc..defda04b 100644
--- a/Package.swift
+++ b/Package.swift
@@ -27,10 +27,9 @@ swiftSettings.append(
 
 // Strict concurrency is enabled in CI; use this environment variable to enable it locally.
 if ProcessInfo.processInfo.environment["SWIFT_OPENAPI_STRICT_CONCURRENCY"].flatMap(Bool.init) ?? false {
-    #warning("Compiling with Strict Concurrency")
     swiftSettings.append(contentsOf: [
+        .define("SWIFT_OPENAPI_STRICT_CONCURRENCY"),
         .enableExperimentalFeature("StrictConcurrency"),
-        .unsafeFlags(["-warnings-as-errors"]),
     ])
 }
 #endif
diff --git a/Sources/_OpenAPIGeneratorCore/PlatformChecks.swift b/Sources/_OpenAPIGeneratorCore/PlatformChecks.swift
index 7b8cd14e..01bf66c4 100644
--- a/Sources/_OpenAPIGeneratorCore/PlatformChecks.swift
+++ b/Sources/_OpenAPIGeneratorCore/PlatformChecks.swift
@@ -17,3 +17,7 @@
 #if !(os(macOS) || os(Linux))
 #error("_OpenAPIGeneratorCore is only to be used by swift-openapi-generator itself—your target should not link this library or the command line tool directly.")
 #endif
+
+#if SWIFT_OPENAPI_STRICT_CONCURRENCY
+#warning("Compiling with Strict Concurrency")
+#endif