diff --git a/modules/openapi-generator/src/main/resources/swift5/Models.mustache b/modules/openapi-generator/src/main/resources/swift5/Models.mustache
index 4e839503b4d..9a3f50d5d8e 100644
--- a/modules/openapi-generator/src/main/resources/swift5/Models.mustache
+++ b/modules/openapi-generator/src/main/resources/swift5/Models.mustache
@@ -46,7 +46,7 @@ protocol JSONEncodable {
         let rawHeader = response.allHeaderFields
         var header = [String:String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models.swift
index 73a987d3e2f..6089ac67d0d 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ internal class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }
diff --git a/samples/client/test/swift5/default/TestClient/Classes/OpenAPIs/Models.swift b/samples/client/test/swift5/default/TestClient/Classes/OpenAPIs/Models.swift
index b0bfb115976..c0542c14c08 100644
--- a/samples/client/test/swift5/default/TestClient/Classes/OpenAPIs/Models.swift
+++ b/samples/client/test/swift5/default/TestClient/Classes/OpenAPIs/Models.swift
@@ -45,7 +45,7 @@ open class Response<T> {
         let rawHeader = response.allHeaderFields
         var header = [String: String]()
         for (key, value) in rawHeader {
-            if let key = key as? String, let value = value as? String {
+            if let key = key.base as? String, let value = value as? String {
                 header[key] = value
             }
         }