diff --git a/lib/private/Memcache/KeyValueCache.php b/lib/private/Memcache/KeyValueCache.php
index 9125290d801f4..c3b1083e5d3d2 100644
--- a/lib/private/Memcache/KeyValueCache.php
+++ b/lib/private/Memcache/KeyValueCache.php
@@ -242,13 +242,13 @@ private function normalizeTtl(int $ttl): int {
 	 * Serialize a value for storage in the key-value store.
 	 */
 	protected static function encodeValue(mixed $value): string {
-		return is_int($value) ? (string)$value : json_encode($value, JSON_THROW_ON_ERROR);
+		return is_int($value) ? (string)$value : json_encode($value, JSON_THROW_ON_ERROR | JSON_PRESERVE_ZERO_FRACTION);
 	}
 
 	/**
 	 * Unserialize a value from the key-value store.
 	 */
 	protected static function decodeValue(string $value): mixed {
-		return is_numeric($value) ? (int)$value : json_decode($value, true);
+		return json_decode($value, true, 512, JSON_THROW_ON_ERROR);
 	}
 }
diff --git a/lib/private/Memcache/Redis.php b/lib/private/Memcache/Redis.php
index afd813921e7be..6d41f517a66ab 100644
--- a/lib/private/Memcache/Redis.php
+++ b/lib/private/Memcache/Redis.php
@@ -233,10 +233,10 @@ protected function evalLua(string $scriptName, array $keys, array $args) {
 	}
 
 	protected static function encodeValue(mixed $value): string {
-		return is_int($value) ? (string)$value : json_encode($value);
+		return is_int($value) ? (string)$value : json_encode($value, JSON_THROW_ON_ERROR | JSON_PRESERVE_ZERO_FRACTION);
 	}
 
 	protected static function decodeValue(string $value): mixed {
-		return is_numeric($value) ? (int)$value : json_decode($value, true);
+		return json_decode($value, true, 512, JSON_THROW_ON_ERROR);
 	}
 }
diff --git a/tests/lib/Memcache/Cache.php b/tests/lib/Memcache/Cache.php
index a4268a36c5371..dce755793fab5 100644
--- a/tests/lib/Memcache/Cache.php
+++ b/tests/lib/Memcache/Cache.php
@@ -16,6 +16,40 @@ abstract class Cache extends \Test\Cache\TestCache {
 	 */
 	protected $instance;
 
+	/**
+	 * @return array<string, array{0: mixed}>
+ 	*/
+	public static function roundtripValuesProvider(): array {
+		return [
+			'string' => ['some string value'],
+			'empty string' => [''],
+			'numeric string' => ['0123'],
+			'float-like string' => ['3.14'],
+			'scientific notation string' => ['1e3'],
+			'integer' => [1234],
+			'zero' => [0],
+			'negative integer' => [-42],
+			'float' => [3.14],
+			'zero-fraction float' => [1.0],
+			'negative float' => [-2.75],
+			'scientific notation float' => [1.2e3],
+			'boolean true' => [true],
+			'boolean false' => [false],
+			'null' => [null],
+			'list' => [['a', 'b', 'c']],
+			'associative array' => [['foo' => 'bar', 'baz' => 42]],
+			'mixed nested array' => [[
+				'int' => 7,
+				'float' => 3.14,
+				'whole-float' => 1.0,
+				'string' => '3.14',
+				'bool' => true,
+				'null' => null,
+				'list' => [1, 2.5, '3'],
+			]],
+		];
+	}
+
 	public function testExistsAfterSet(): void {
 		$this->assertFalse($this->instance->hasKey('foo'));
 		$this->instance->set('foo', 'bar');
@@ -34,6 +68,15 @@ public function testGetArrayAfterSet(): void {
 		$this->assertEquals(['bar'], $this->instance->get('foo'));
 	}
 
+	#[\PHPUnit\Framework\Attributes\DataProvider('roundtripValuesProvider')]
+	public function testStoreAndReadBack(mixed $value): void {
+		$this->assertNull($this->instance->get('roundtrip'), 'key should be empty before storing');
+
+		$this->assertNotFalse($this->instance->set('roundtrip', $value), 'value should be stored');
+		$this->assertTrue($this->instance->hasKey('roundtrip'), 'stored key should exist');
+		$this->assertSame($value, $this->instance->get('roundtrip'), 'stored value should be read back unchanged');
+	}
+
 	public function testDoesNotExistAfterRemove(): void {
 		$this->instance->set('foo', 'bar');
 		$this->instance->remove('foo');