diff --git a/typo3/sysext/core/Classes/Routing/Enhancer/VariableProcessor.php b/typo3/sysext/core/Classes/Routing/Enhancer/VariableProcessor.php
index 308f4541a4e11bced978c7ae278c49f231601eec..9cf3a94f8bf30e39e8cd26d3b1082a17cfd7b165 100644
--- a/typo3/sysext/core/Classes/Routing/Enhancer/VariableProcessor.php
+++ b/typo3/sysext/core/Classes/Routing/Enhancer/VariableProcessor.php
@@ -280,6 +280,7 @@ class VariableProcessor
             return $values;
         }
         $namespacePrefix = $namespace ? $namespace . static::LEVEL_DELIMITER : '';
+        $arguments = array_map('strval', $arguments);
         return array_map(
             function (string $value) use ($arguments, $namespacePrefix, $hash) {
                 $value = $arguments[$value] ?? $value;
@@ -308,6 +309,7 @@ class VariableProcessor
         if (empty($values) || empty($arguments) && empty($namespace)) {
             return $values;
         }
+        $arguments = array_map('strval', $arguments);
         $namespacePrefix = $namespace ? $namespace . static::LEVEL_DELIMITER : '';
         return array_map(
             function (string $value) use ($arguments, $namespacePrefix, $hash) {
@@ -318,7 +320,7 @@ class VariableProcessor
                     $value = substr($value, strlen($namespacePrefix));
                 }
                 $value = $this->resolveNestedValue($value);
-                $index = array_search($value, $arguments);
+                $index = array_search($value, $arguments, true);
                 return $index !== false ? $index : $value;
             },
             $values
@@ -342,7 +344,7 @@ class VariableProcessor
         $result = [];
         foreach ($array as $key => $value) {
             if (is_array($value)) {
-                $result = array_merge(
+                $result = array_replace(
                     $result,
                     $this->deflateArray(
                         $value,
@@ -369,8 +371,8 @@ class VariableProcessor
     {
         $result = [];
         foreach ($array as $key => $value) {
-            $inflatedKey = $this->resolveHash($key);
-            // inflate nested values `namespace__any__neste` -> `namespace__any/nested`
+            $inflatedKey = $this->resolveHash((string)$key);
+            // inflate nested values `namespace__any__nested` -> `namespace__any/nested`
             $inflatedKey = $this->inflateNestedValue($inflatedKey, $namespace, $arguments);
             $steps = explode(static::LEVEL_DELIMITER, $inflatedKey);
             $pointer = &$result;
@@ -395,9 +397,10 @@ class VariableProcessor
         if (!empty($namespace) && strpos($value, $namespacePrefix) !== 0) {
             return $value;
         }
+        $arguments = array_map('strval', $arguments);
         $possibleNestedValueKey = substr($value, strlen($namespacePrefix));
         $possibleNestedValue = $this->nestedValues[$possibleNestedValueKey] ?? null;
-        if (!$possibleNestedValue || !in_array($possibleNestedValue, $arguments, true)) {
+        if ($possibleNestedValue === null || !in_array($possibleNestedValue, $arguments, true)) {
             return $value;
         }
         return $namespacePrefix . $possibleNestedValue;
diff --git a/typo3/sysext/core/Tests/Unit/Routing/Enhancer/VariableProcessorTest.php b/typo3/sysext/core/Tests/Unit/Routing/Enhancer/VariableProcessorTest.php
index 34ca8ed366d5f6dc7c0cf181beb186d3244a8b25..139ceceec2d10cb7a8425016b6fcb7dc4618860b 100644
--- a/typo3/sysext/core/Tests/Unit/Routing/Enhancer/VariableProcessorTest.php
+++ b/typo3/sysext/core/Tests/Unit/Routing/Enhancer/VariableProcessorTest.php
@@ -56,6 +56,12 @@ class VariableProcessorTest extends UnitTestCase
                 $enforcedInflatedRoutePath,
                 '/static/{!aa}/{bb}/{some_cc}/tail'
             ],
+            'aa -> 1, no namespace (plain)' => [
+                null,
+                ['aa' => 1],
+                $plainInflatedRoutePath,
+                '/static/{1}/{bb}/{some_cc}/tail'
+            ],
             'aa -> zz, no namespace (plain)' => [
                 null,
                 ['aa' => 'zz'],
@@ -166,6 +172,10 @@ class VariableProcessorTest extends UnitTestCase
                 ['a' => 'newA'],
                 ['newA' => 'a', 'first__aa' => 'aa', 'first__second__aaa' => 'aaa', 'a9d66412d169b85537e11d9e49b75f9' => '@any']
             ],
+            'no namespace, a -> 1' => [
+                ['a' => 1],
+                [1 => 'a', 'first__aa' => 'aa', 'first__second__aaa' => 'aaa', 'a9d66412d169b85537e11d9e49b75f9' => '@any']
+            ],
             'no namespace, a -> @any/nested' => [
                 ['a' => '@any/nested'],
                 ['qbeced67e6b340abc67a397f6e90bb0' => 'a', 'first__aa' => 'aa', 'first__second__aaa' => 'aaa', 'a9d66412d169b85537e11d9e49b75f9' => '@any']
@@ -205,6 +215,11 @@ class VariableProcessorTest extends UnitTestCase
                 [],
                 ['a' => 'a', 'first' => ['aa' => 'aa', 'second' => ['aaa' => 'aaa', '@any' => '@any']]]
             ],
+            'no namespace, a -> 1' => [
+                '',
+                ['a' => 1],
+                ['a' => 'a', 'first' => ['aa' => 'aa', 'second' => ['aaa' => 'aaa', '@any' => '@any']]]
+            ],
             'no namespace, a -> newA' => [
                 '',
                 ['a' => 'newA'],
@@ -286,6 +301,11 @@ class VariableProcessorTest extends UnitTestCase
                 [],
                 ['a' => 'a', 'b' => 'b', 'c' => ['d' => 'd', 'e' => 'e']]
             ],
+            'a -> 1, no namespace' => [
+                null,
+                ['a' => 1],
+                [1 => 'a', 'b' => 'b', 'c' => ['d' => 'd', 'e' => 'e']]
+            ],
             'a -> newA, no namespace' => [
                 null,
                 ['a' => 'newA'],