diff --git a/apps/workflowengine/lib/Check/FileSize.php b/apps/workflowengine/lib/Check/FileSize.php
index 9fcac0c98562b..aa2bb9279906d 100644
--- a/apps/workflowengine/lib/Check/FileSize.php
+++ b/apps/workflowengine/lib/Check/FileSize.php
@@ -14,9 +14,9 @@
 
 class FileSize implements ICheck {
 
-	/** @var int */
-	protected $size;
-
+	/** @var int|float|null */
+	protected int|float|null $size;
+	
 	/** @var IL10N */
 	protected $l;
 
@@ -72,25 +72,35 @@ public function validateCheck($operator, $value) {
 	}
 
 	/**
-	 * @return string
+	 * Gets the file size from HTTP headers.
+	 *
+	 * Checks 'OC-Total-Length' first; if unavailable and the method is POST or PUT,
+	 * checks 'Content-Length'. Returns the size as int, float, or false if not found or invalid.
+	 *
+	 * @return int|float|false File size in bytes, or false if unavailable.
 	 */
 	protected function getFileSizeFromHeader() {
 		if ($this->size !== null) {
+			// Already have it cached?
 			return $this->size;
 		}
 
 		$size = $this->request->getHeader('OC-Total-Length');
 		if ($size === '') {
-			if (in_array($this->request->getMethod(), ['POST', 'PUT'])) {
+			// Try fallback for upload methods
+			$method = $this->request->getMethod();
+			if (in_array($method, ['POST', 'PUT'], true)) {
 				$size = $this->request->getHeader('Content-Length');
 			}
 		}
 
-		if ($size === '') {
-			$size = false;
+		if ($size !== '' && is_numeric($size)) {
+			$this->size = Util::numericToNumber($size);
+		} else {
+			// No valid size header found
+			$this->size = false;
 		}
 
-		$this->size = $size;
 		return $this->size;
 	}
 
diff --git a/build/psalm-baseline.xml b/build/psalm-baseline.xml
index 8ce1af0776e41..6991f790d7e28 100644
--- a/build/psalm-baseline.xml
+++ b/build/psalm-baseline.xml
@@ -1212,20 +1212,6 @@
       <code><![CDATA[null]]></code>
     </NullArgument>
   </file>
-  <file src="apps/workflowengine/lib/Check/FileSize.php">
-    <FalsableReturnStatement>
-      <code><![CDATA[$this->size]]></code>
-    </FalsableReturnStatement>
-    <InvalidPropertyAssignmentValue>
-      <code><![CDATA[$size]]></code>
-    </InvalidPropertyAssignmentValue>
-    <InvalidReturnStatement>
-      <code><![CDATA[$this->size]]></code>
-    </InvalidReturnStatement>
-    <InvalidReturnType>
-      <code><![CDATA[string]]></code>
-    </InvalidReturnType>
-  </file>
   <file src="apps/workflowengine/lib/Check/RequestRemoteAddress.php">
     <InvalidArgument>
       <code><![CDATA[$decodedValue[1]]]></code>