diff --git a/src/main/java/org/elasticsearch/cluster/metadata/MetaData.java b/src/main/java/org/elasticsearch/cluster/metadata/MetaData.java
index 7dfa3641e87..81ed30c6ee4 100644
--- a/src/main/java/org/elasticsearch/cluster/metadata/MetaData.java
+++ b/src/main/java/org/elasticsearch/cluster/metadata/MetaData.java
@@ -1329,7 +1329,7 @@ public class MetaData implements Iterable<IndexMetaData>, Diffable<MetaData> {
                     continue;
                 }
                 // It's a naked number that previously would be interpreted as default unit (bytes); now we add it:
-                logger.warn("byte-sized cluster setting [{}] with value [{}] is missing units; now adding default units (b)", settingName, settingValue);
+                logger.warn("byte-sized cluster setting [{}] with value [{}] is missing units; assuming default units (b) but in future versions this will be a hard error", settingName, settingValue);
                 if (newPersistentSettings == null) {
                     newPersistentSettings = Settings.builder();
                     newPersistentSettings.put(metaData.persistentSettings());
@@ -1343,7 +1343,7 @@ public class MetaData implements Iterable<IndexMetaData>, Diffable<MetaData> {
                     continue;
                 }
                 // It's a naked number that previously would be interpreted as default unit (ms); now we add it:
-                logger.warn("time cluster setting [{}] with value [{}] is missing units; now adding default units (ms)", settingName, settingValue);
+                logger.warn("time cluster setting [{}] with value [{}] is missing units; assuming default units (ms) but in future versions this will be a hard error", settingName, settingValue);
                 if (newPersistentSettings == null) {
                     newPersistentSettings = Settings.builder();
                     newPersistentSettings.put(metaData.persistentSettings());
diff --git a/src/main/java/org/elasticsearch/cluster/metadata/MetaDataIndexUpgradeService.java b/src/main/java/org/elasticsearch/cluster/metadata/MetaDataIndexUpgradeService.java
index 8a58a56e60e..84c13980939 100644
--- a/src/main/java/org/elasticsearch/cluster/metadata/MetaDataIndexUpgradeService.java
+++ b/src/main/java/org/elasticsearch/cluster/metadata/MetaDataIndexUpgradeService.java
@@ -191,7 +191,7 @@ public class MetaDataIndexUpgradeService extends AbstractComponent {
                         continue;
                     }
                     // It's a naked number that previously would be interpreted as default unit (bytes); now we add it:
-                    logger.warn("byte-sized index setting [{}] with value [{}] is missing units; now adding default units (b)", byteSizeSetting, value);
+                    logger.warn("byte-sized index setting [{}] with value [{}] is missing units; assuming default units (b) but in future versions this will be a hard error", byteSizeSetting, value);
                     if (newSettings == null) {
                         newSettings = Settings.builder();
                         newSettings.put(settings);
@@ -208,7 +208,7 @@ public class MetaDataIndexUpgradeService extends AbstractComponent {
                         continue;
                     }
                     // It's a naked number that previously would be interpreted as default unit (ms); now we add it:
-                    logger.warn("time index setting [{}] with value [{}] is missing units; now adding default units (ms)", timeSetting, value);
+                    logger.warn("time index setting [{}] with value [{}] is missing units; assuming default units (ms) but in future versions this will be a hard error", timeSetting, value);
                     if (newSettings == null) {
                         newSettings = Settings.builder();
                         newSettings.put(settings);