diff --git a/extensions/ter_fe2/Classes/Validation/Validator/TokenCreationValidator.php b/extensions/ter_fe2/Classes/Validation/Validator/TokenCreationValidator.php
index b77df3b9e4b36f1e1662a47f44be68ba7e399ee9..59a011b00e9331dd9ec05eba6e889d7fd427a653 100644
--- a/extensions/ter_fe2/Classes/Validation/Validator/TokenCreationValidator.php
+++ b/extensions/ter_fe2/Classes/Validation/Validator/TokenCreationValidator.php
@@ -76,11 +76,7 @@ class TokenCreationValidator extends AbstractValidator
 
         if ($value->getExtensions() !== []) {
             foreach ($value->getExtensions() as $extension) {
-                $length = strlen(trim($extension));
-                if ($length < 3
-                    || $length > 30
-                    || !(bool)preg_match('/^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z]{1}[a-z0-9_]+)$/', $extension)
-                ) {
+                if (!(bool)preg_match('/^[a-z][a-z0-9_]{2,29}$/', $extension)) {
                     $this->addError($extension . ' is no valid extension key', 1605034751);
                     return false;
                 }
diff --git a/extensions/ter_fe2/Tests/Unit/Validation/TokenCreatingValidatorTest.php b/extensions/ter_fe2/Tests/Unit/Validation/TokenCreatingValidatorTest.php
index 1499906802173560d1d281fffd5871c23b93df1a..a2257da25ab81fa0ac3848e47d9024ec0bca7305 100644
--- a/extensions/ter_fe2/Tests/Unit/Validation/TokenCreatingValidatorTest.php
+++ b/extensions/ter_fe2/Tests/Unit/Validation/TokenCreatingValidatorTest.php
@@ -111,7 +111,7 @@ class TokenCreatingValidatorTest extends AbstractTestCase
             1605034751
         ];
         yield 'Invalid extension name 2' => [
-            ['password', '', null, [], ['valid_ext', 'tx_ext']],
+            ['password', '', null, [], ['valid_ext', '_ext']],
             1605034751
         ];
         yield 'Invalid extension name 3' => [
diff --git a/extensions/ter_rest/Resources/Private/Schema/v1.json b/extensions/ter_rest/Resources/Private/Schema/v1.json
index 1cd9177411895efa5529f0c7299e92104989ce8b..01730ae7aaf563e4cb806cb3e61035c0fb1392af 100644
--- a/extensions/ter_rest/Resources/Private/Schema/v1.json
+++ b/extensions/ter_rest/Resources/Private/Schema/v1.json
@@ -228,7 +228,7 @@
               "items": {
                 "maxLength": 30,
                 "minLength": 3,
-                "pattern": "^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z]{1}[a-z0-9_]+)$",
+                "pattern": "^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z][a-z0-9_]+)$",
                 "type": "string"
               }
             },
@@ -837,7 +837,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -965,7 +965,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1097,7 +1097,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1237,7 +1237,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1360,7 +1360,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1490,7 +1490,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1644,7 +1644,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1787,7 +1787,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -1965,7 +1965,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -2103,7 +2103,7 @@
             "schema": {
               "maxLength": 30,
               "minLength": 3,
-              "pattern": "^[a-z]{1}[a-z0-9_]+$",
+              "pattern": "^[a-z][a-z0-9_]+$",
               "type": "string"
             },
             "example": "my_typo3_extension"
@@ -3070,7 +3070,7 @@
         "schema": {
           "maxLength": 30,
           "minLength": 3,
-          "pattern": "^[a-z]{1}[a-z0-9_]+$",
+          "pattern": "^[a-z][a-z0-9_]+$",
           "type": "string"
         },
         "example": "my_typo3_extension"
@@ -3246,7 +3246,7 @@
           "items": {
             "maxLength": 30,
             "minLength": 3,
-            "pattern": "^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z]{1}[a-z0-9_]+)$",
+            "pattern": "^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z][a-z0-9_]+)$",
             "type": "string"
           }
         },
diff --git a/extensions/ter_rest/Resources/Private/Schema/v1.yaml b/extensions/ter_rest/Resources/Private/Schema/v1.yaml
index fdad84959d109e4e805c26e5282c5765cb4c593a..e897836b077d2a186f8c3d8b6817467ee12730d4 100644
--- a/extensions/ter_rest/Resources/Private/Schema/v1.yaml
+++ b/extensions/ter_rest/Resources/Private/Schema/v1.yaml
@@ -162,7 +162,7 @@ paths:
           items:
             maxLength: 30
             minLength: 3
-            pattern: ^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z]{1}[a-z0-9_]+)$
+            pattern: ^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z][a-z0-9_]+)$
             type: string
         example: my_new_extension,another_awesome_extension
       responses:
@@ -557,7 +557,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       responses:
@@ -636,7 +636,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       requestBody:
@@ -718,7 +718,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       responses:
@@ -806,7 +806,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       responses:
@@ -882,7 +882,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       responses:
@@ -962,7 +962,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       - name: username
@@ -1060,7 +1060,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       - name: version
@@ -1151,7 +1151,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       - name: version
@@ -1264,7 +1264,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       - name: version
@@ -1352,7 +1352,7 @@ paths:
         schema:
           maxLength: 30
           minLength: 3
-          pattern: ^[a-z]{1}[a-z0-9_]+$
+          pattern: ^[a-z][a-z0-9_]+$
           type: string
         example: my_typo3_extension
       - name: version
@@ -2002,7 +2002,7 @@ components:
       schema:
         maxLength: 30
         minLength: 3
-        pattern: ^[a-z]{1}[a-z0-9_]+$
+        pattern: ^[a-z][a-z0-9_]+$
         type: string
       example: my_typo3_extension
     Username:
@@ -2149,7 +2149,7 @@ components:
         items:
           maxLength: 30
           minLength: 3
-          pattern: ^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z]{1}[a-z0-9_]+)$
+          pattern: ^((?!(tx|user|pages|tt|sys|ts_language|csh))[a-z][a-z0-9_]+)$
           type: string
       example: my_new_extension,another_awesome_extension
   requestBodies:
diff --git a/extensions/ter_rest/Tests/Unit/Routing/RouteArgument/RouteArgumentFactoryTest.php b/extensions/ter_rest/Tests/Unit/Routing/RouteArgument/RouteArgumentFactoryTest.php
index 32880f26e0fe50b9e11786807606ad204b71c077..41a57851c02d467422f904c168a650a791504b3c 100644
--- a/extensions/ter_rest/Tests/Unit/Routing/RouteArgument/RouteArgumentFactoryTest.php
+++ b/extensions/ter_rest/Tests/Unit/Routing/RouteArgument/RouteArgumentFactoryTest.php
@@ -106,7 +106,7 @@ class RouteArgumentFactoryTest extends AbstractTestCase
             $this->getStringArgumentConfiguration(['value' => '12345foobar']),
             '{"name":"key","value":"12345foobar","validationErrors":["The given value \'12345foobar\' for argument \'key\''
             . ' must be at max 10 chars long.","The given value \'12345foobar\' for argument \'key\' does not match the pattern:'
-            . ' ^[a-z]{1}[a-z0-9_]+$"]}',
+            . ' ^[a-z][a-z0-9_]+$"]}',
             0
         ];
         yield 'StringArgument Invalid (wrong type)' => [
@@ -198,7 +198,7 @@ class RouteArgumentFactoryTest extends AbstractTestCase
                         'type' => 'string',
                         'minLength' => 1,
                         'maxLength' => 10,
-                        'pattern' => '^[a-z]{1}[a-z0-9_]+$'
+                        'pattern' => '^[a-z][a-z0-9_]+$'
                     ]
                 ]
             ],