diff --git a/direct/core/src/main/java/cz/o2/proxima/direct/core/transaction/TransactionalOnlineAttributeWriter.java b/direct/core/src/main/java/cz/o2/proxima/direct/core/transaction/TransactionalOnlineAttributeWriter.java
index 6f9fe9b80..ceb18bb90 100644
--- a/direct/core/src/main/java/cz/o2/proxima/direct/core/transaction/TransactionalOnlineAttributeWriter.java
+++ b/direct/core/src/main/java/cz/o2/proxima/direct/core/transaction/TransactionalOnlineAttributeWriter.java
@@ -252,6 +252,15 @@ public void commitWrite(List<StreamElement> outputs, CommitCallback callback)
           transformed.size() == 1 && !isGlobalTransaction ? delegate : commitDelegate;
       List<KeyAttribute> keyAttributes =
           transformed.stream().map(KeyAttributes::ofStreamElement).collect(Collectors.toList());
+      boolean anyDisallowed = keyAttributes.stream().anyMatch(KeyAttribute::isWildcardQuery);
+      if (anyDisallowed) {
+        throw new IllegalArgumentException(
+            String.format(
+                "Invalid output writes %s. Wildcards need to have suffixes.",
+                keyAttributes.stream()
+                    .filter(KeyAttribute::isWildcardQuery)
+                    .collect(Collectors.toList())));
+      }
       manager.commit(transactionId, keyAttributes);
       Response response = takeResponse();
       if (response.getFlags() != Response.Flags.COMMITTED) {
diff --git a/direct/transaction-manager/src/main/java/cz/o2/proxima/direct/transaction/manager/TransactionLogObserver.java b/direct/transaction-manager/src/main/java/cz/o2/proxima/direct/transaction/manager/TransactionLogObserver.java
index 622a96e2a..d2c364177 100644
--- a/direct/transaction-manager/src/main/java/cz/o2/proxima/direct/transaction/manager/TransactionLogObserver.java
+++ b/direct/transaction-manager/src/main/java/cz/o2/proxima/direct/transaction/manager/TransactionLogObserver.java
@@ -510,7 +510,8 @@ static Iterable<KeyAttribute> concatInputsAndOutputs(
                     (a, b) -> a.getSequenceId() < b.getSequenceId() ? a : b));
     outputAttributes.forEach(
         ka -> {
-          Preconditions.checkArgument(!ka.isWildcardQuery());
+          Preconditions.checkArgument(
+              !ka.isWildcardQuery(), "Got KeyAttribute %s, which is not allowed output.", ka);
           KeyWithAttribute kwa = KeyWithAttribute.of(ka);
           if (!ka.getAttributeSuffix().isPresent()) {
             mapOfInputs.putIfAbsent(kwa, ka);