diff --git a/translation-web/src/main/java/eu/europeana/api/translation/web/TranslationController.java b/translation-web/src/main/java/eu/europeana/api/translation/web/TranslationController.java
index f6021ea7..1c9f6c97 100644
--- a/translation-web/src/main/java/eu/europeana/api/translation/web/TranslationController.java
+++ b/translation-web/src/main/java/eu/europeana/api/translation/web/TranslationController.java
@@ -1,6 +1,8 @@
 package eu.europeana.api.translation.web;
 
 import javax.servlet.http.HttpServletRequest;
+
+import org.apache.commons.lang3.StringUtils;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
@@ -10,7 +12,6 @@
 import eu.europeana.api.commons.web.exception.ParamValidationException;
 import eu.europeana.api.commons.web.http.HttpHeaders;
 import eu.europeana.api.commons.web.model.vocabulary.Operations;
-import eu.europeana.api.translation.config.I18nConstants;
 import eu.europeana.api.translation.definitions.language.LanguagePair;
 import eu.europeana.api.translation.definitions.vocabulary.TranslationAppConstants;
 import eu.europeana.api.translation.model.TranslationRequest;
@@ -18,8 +19,11 @@
 import eu.europeana.api.translation.web.service.TranslationWebService;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
+import static eu.europeana.api.translation.config.I18nConstants.EMPTY_PARAM_MANDATORY;
+import static eu.europeana.api.translation.config.I18nConstants.INVALID_SERVICE_PARAM;
+
 @RestController
-@Tag(name = "Translation endoint", description = "Perform text translation")
+@Tag(name = "Translation endpoint", description = "Perform text translation")
 public class TranslationController extends BaseRest {
 
   private final TranslationWebService translationService;
@@ -49,23 +53,19 @@ public ResponseEntity<String> translate(@RequestBody TranslationRequest translRe
   private void validateRequest(TranslationRequest translationRequest) throws ParamValidationException {
     // validate mandatory params
     if (translationRequest.getText() == null) {
-      throw new ParamValidationException( I18nConstants.EMPTY_PARAM_MANDATORY, I18nConstants.EMPTY_PARAM_MANDATORY,
+      throw new ParamValidationException( EMPTY_PARAM_MANDATORY, EMPTY_PARAM_MANDATORY,
           new String[] {TranslationAppConstants.TEXT});
     }
-    //source is optional
-//    if (translRequest.getSource() == null) {
-//      throw new ParamValidationException( I18nConstants.EMPTY_PARAM_MANDATORY, I18nConstants.EMPTY_PARAM_MANDATORY,
-//          new String[] {TranslationAppConstants.SOURCE_LANG});
-//    }
-    if (translationRequest.getTarget() ==  I18nConstants.EMPTY_PARAM_MANDATORY) {
-      throw new ParamValidationException(I18nConstants.EMPTY_PARAM_MANDATORY, I18nConstants.EMPTY_PARAM_MANDATORY,
+
+    if (StringUtils.equals(translationRequest.getTarget(), EMPTY_PARAM_MANDATORY)) {
+      throw new ParamValidationException(EMPTY_PARAM_MANDATORY, EMPTY_PARAM_MANDATORY,
           new String[] {TranslationAppConstants.TARGET_LANG});
     }
     
     //validate language pair
     final LanguagePair languagePair = new LanguagePair(translationRequest.getSource(), translationRequest.getTarget());
     if(!translationService.isTranslationSupported(languagePair)) {
-        throw new ParamValidationException(null, I18nConstants.INVALID_SERVICE_PARAM, new String[] {languagePair.toString()});
+        throw new ParamValidationException(null, INVALID_SERVICE_PARAM, new String[] {languagePair.toString()});
     }
   }