diff --git a/modules/util/source-formatter/src/main/java/com/liferay/source/formatter/check/PropertiesLanguageKeysCheck.java b/modules/util/source-formatter/src/main/java/com/liferay/source/formatter/check/PropertiesLanguageKeysCheck.java
index 4d69ea4784c9ef..10381a86f26751 100644
--- a/modules/util/source-formatter/src/main/java/com/liferay/source/formatter/check/PropertiesLanguageKeysCheck.java
+++ b/modules/util/source-formatter/src/main/java/com/liferay/source/formatter/check/PropertiesLanguageKeysCheck.java
@@ -93,7 +93,8 @@ protected String doProcess(
 		return content;
 	}
 
-	private Properties _getPortalLanguageProperties(String absolutePath)
+	private synchronized Properties _getPortalLanguageProperties(
+			String absolutePath)
 		throws IOException {
 
 		String portalLanguagePropertiesFileName = getAttributeValue(