diff --git a/eu_basynthec/dist/etc/growth-profiles/data-set-validator.py b/eu_basynthec/dist/etc/growth-profiles/data-set-validator.py
index ec1e5b7039d207fd95cf8747d18296d0acfe713d..c09a86937a65acebfb74653345354dad5a569e7c 100644
--- a/eu_basynthec/dist/etc/growth-profiles/data-set-validator.py
+++ b/eu_basynthec/dist/etc/growth-profiles/data-set-validator.py
@@ -85,7 +85,7 @@ class ValidationHelper:
 
 	def checkIsSpecified(self, property, displayName):
 		if self.metadataMap.get(property) is None:
-			errors.add(ValidationError.createFileValidationError("A " + displayName
+			self.errors.append(ValidationError.createFileValidationError("A " + displayName
 					+ " must be specified."))
 			return False
 		return True
diff --git a/eu_basynthec/dist/etc/metabolomics/data-set-validator.py b/eu_basynthec/dist/etc/metabolomics/data-set-validator.py
index 5cb73b9af6813199abea7e1447c24280fadfa87a..e6e549068a48c1f997516173276b87809cdd84fc 100644
--- a/eu_basynthec/dist/etc/metabolomics/data-set-validator.py
+++ b/eu_basynthec/dist/etc/metabolomics/data-set-validator.py
@@ -85,7 +85,7 @@ class ValidationHelper:
 
 	def checkIsSpecified(self, property, displayName):
 		if self.metadataMap.get(property) is None:
-			errors.add(ValidationError.createFileValidationError("A " + displayName
+			self.errors.append(ValidationError.createFileValidationError("A " + displayName
 					+ " must be specified."))
 			return False
 		return True
diff --git a/eu_basynthec/dist/etc/proteomics/data-set-validator.py b/eu_basynthec/dist/etc/proteomics/data-set-validator.py
index 7ac5a1789b080a4c14c083982a490b1a3f1710f7..c1150d736ebceb5234e38ff17f84daa1ba3a9d74 100644
--- a/eu_basynthec/dist/etc/proteomics/data-set-validator.py
+++ b/eu_basynthec/dist/etc/proteomics/data-set-validator.py
@@ -85,7 +85,7 @@ class ValidationHelper:
 
 	def checkIsSpecified(self, property, displayName):
 		if self.metadataMap.get(property) is None:
-			errors.add(ValidationError.createFileValidationError("A " + displayName
+			self.errors.append(ValidationError.createFileValidationError("A " + displayName
 					+ " must be specified."))
 			return False
 		return True
diff --git a/eu_basynthec/dist/etc/transcriptomics/data-set-validator.py b/eu_basynthec/dist/etc/transcriptomics/data-set-validator.py
index 8e1acaeb74b372bf3ec729e9ff11e0743594e359..5cdf0840db0c90ff7924b16fc815d952788a3528 100644
--- a/eu_basynthec/dist/etc/transcriptomics/data-set-validator.py
+++ b/eu_basynthec/dist/etc/transcriptomics/data-set-validator.py
@@ -85,7 +85,7 @@ class ValidationHelper:
 
 	def checkIsSpecified(self, property, displayName):
 		if self.metadataMap.get(property) is None:
-			errors.add(ValidationError.createFileValidationError("A " + displayName
+			self.errors.append(ValidationError.createFileValidationError("A " + displayName
 					+ " must be specified."))
 			return False
 		return True