diff --git a/core/src/main/java/org/elasticsearch/index/translog/Translog.java b/core/src/main/java/org/elasticsearch/index/translog/Translog.java
index 00fc4556d05..0d2fba6ea57 100644
--- a/core/src/main/java/org/elasticsearch/index/translog/Translog.java
+++ b/core/src/main/java/org/elasticsearch/index/translog/Translog.java
@@ -173,10 +173,10 @@ public class Translog extends AbstractIndexShardComponent implements IndexShardC
                 //
                 // For this to happen we must have already copied the translog.ckp file into translog-gen.ckp so we first check if that file exists
                 // if not we don't even try to clean it up and wait until we fail creating it
-                assert Files.exists(nextTranslogFile) == false || Files.size(nextTranslogFile) <= TranslogWriter.getHeaderLength(translogUUID);
+                assert Files.exists(nextTranslogFile) == false || Files.size(nextTranslogFile) <= TranslogWriter.getHeaderLength(translogUUID) : "unexpected translog file: [" + nextTranslogFile + "]";
                 if (Files.exists(currentCheckpointFile) // current checkpoint is already copied
                     && Files.deleteIfExists(nextTranslogFile)) { // delete it and log a warning
-                    logger.warn("Deleted invalid next generation before opening writer {} this is like caused by some previously tragic exception ", nextTranslogFile.getFileName());
+                    logger.warn("deleted previously created, but not yet committed, next generation [{}]. This can happen due to a tragic exception when creating a new generation", nextTranslogFile.getFileName());
                 }
                 this.recoveredTranslogs = recoverFromFiles(translogGeneration, checkpoint);
                 if (recoveredTranslogs.isEmpty()) {