diff --git a/modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache b/modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache
index 381fddcc81f..ed89576c8a3 100644
--- a/modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache
+++ b/modules/swagger-codegen/src/main/resources/swift4/AlamofireImplementations.mustache
@@ -19,6 +19,8 @@ class AlamofireRequestBuilderFactory: RequestBuilderFactory {
 
 // Store manager to retain its reference
 private var managerStore: [String: Alamofire.SessionManager] = [:]
+// Concurrent queue to save sessionmanagers thread safe
+private let concurrentQueue = DispatchQueue(label: "concurrentQueue", attributes: .concurrent)
 
 open class AlamofireRequestBuilder<T>: RequestBuilder<T> {
     required public init(method: String, URLString: String, parameters: [String : Any]?, isBody: Bool, headers: [String : String] = [:]) {
@@ -58,7 +60,9 @@ open class AlamofireRequestBuilder<T>: RequestBuilder<T> {
         let managerId:String = UUID().uuidString
         // Create a new manager for each request to customize its request header
         let manager = createSessionManager()
-        managerStore[managerId] = manager
+        concurrentQueue.async(flags: .barrier) {
+            managerStore[managerId] = manager
+        }
 
         let encoding:ParameterEncoding = isBody ? JSONDataEncoding() : URLEncoding()
 
@@ -112,7 +116,9 @@ open class AlamofireRequestBuilder<T>: RequestBuilder<T> {
         }
 
         let cleanupRequest = {
-            _ = managerStore.removeValue(forKey: managerId)
+            concurrentQueue.async(flags: .barrier) {
+                _ = managerStore.removeValue(forKey: managerId)
+            }
         }
 
         let validatedRequest = request.validate()
@@ -314,7 +320,9 @@ open class AlamofireDecodableRequestBuilder<T:Decodable>: AlamofireRequestBuilde
         }
 
         let cleanupRequest = {
-            _ = managerStore.removeValue(forKey: managerId)
+            concurrentQueue.async(flags: .barrier) {
+                _ = managerStore.removeValue(forKey: managerId)
+            }
         }
 
         let validatedRequest = request.validate()