diff --git a/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/basic_auth.mustache b/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/basic_auth.mustache
index c2a4426937da..c51c5c23cc71 100644
--- a/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/basic_auth.mustache
+++ b/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/basic_auth.mustache
@@ -19,7 +19,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/bearer_auth.mustache b/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/bearer_auth.mustache
index b4bce45ca61f..b18510385915 100644
--- a/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/bearer_auth.mustache
+++ b/modules/openapi-generator/src/main/resources/dart/libraries/dio/auth/bearer_auth.mustache
@@ -10,7 +10,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/basic_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/basic_auth.dart
index b6e6dce04f9c..b65ccb5b71f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/basic_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/basic_auth.dart
@@ -22,7 +22,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/bearer_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/bearer_auth.dart
index 1d4402b376c0..8f46678761b2 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/bearer_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof/lib/src/auth/bearer_auth.dart
@@ -13,7 +13,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/basic_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/basic_auth.dart
index b6e6dce04f9c..b65ccb5b71f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/basic_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/basic_auth.dart
@@ -22,7 +22,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/bearer_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/bearer_auth.dart
index 1d4402b376c0..8f46678761b2 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/bearer_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/src/auth/bearer_auth.dart
@@ -13,7 +13,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/basic_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/basic_auth.dart
index b6e6dce04f9c..b65ccb5b71f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/basic_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/basic_auth.dart
@@ -22,7 +22,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/bearer_auth.dart b/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/bearer_auth.dart
index 1d4402b376c0..8f46678761b2 100644
--- a/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/bearer_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/oneof_primitive/lib/src/auth/bearer_auth.dart
@@ -13,7 +13,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/basic_auth.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/basic_auth.dart
index b6e6dce04f9c..b65ccb5b71f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/basic_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/basic_auth.dart
@@ -22,7 +22,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/bearer_auth.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/bearer_auth.dart
index 1d4402b376c0..8f46678761b2 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/bearer_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/auth/bearer_auth.dart
@@ -13,7 +13,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/basic_auth.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/basic_auth.dart
index b6e6dce04f9c..b65ccb5b71f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/basic_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/basic_auth.dart
@@ -22,7 +22,7 @@ class BasicAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme'] == 'basic') || secure['type'] == 'basic');
+    final metadataAuthInfo = getAuthInfo(options, (secure) => (secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'basic') || secure['type'] == 'basic');
     for (final info in metadataAuthInfo) {
       final authName = info['name'] as String;
       final basicAuthInfo = authInfo[authName];
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/bearer_auth.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/bearer_auth.dart
index 1d4402b376c0..8f46678761b2 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/bearer_auth.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake/lib/src/auth/bearer_auth.dart
@@ -13,7 +13,7 @@ class BearerAuthInterceptor extends AuthInterceptor {
     RequestOptions options,
     RequestInterceptorHandler handler,
   ) {
-    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme'] == 'bearer');
+    final authInfo = getAuthInfo(options, (secure) => secure['type'] == 'http' && secure['scheme']?.toLowerCase() == 'bearer');
     for (final info in authInfo) {
       final token = tokens[info['name']];
       if (token != null) {