diff --git a/Core/src/main/java/com/intellectualcrafters/plot/util/UUIDHandlerImplementation.java b/Core/src/main/java/com/intellectualcrafters/plot/util/UUIDHandlerImplementation.java
index 215eaf37c..e2f6a047e 100644
--- a/Core/src/main/java/com/intellectualcrafters/plot/util/UUIDHandlerImplementation.java
+++ b/Core/src/main/java/com/intellectualcrafters/plot/util/UUIDHandlerImplementation.java
@@ -134,6 +134,26 @@ public abstract class UUIDHandlerImplementation {
                     }
                 }
             });
+        } else if (Settings.UUID.FORCE_LOWERCASE && !this.unknown.isEmpty() && !name.value.equals(name.value.toLowerCase())) {
+            TaskManager.runTaskAsync(new Runnable() {
+                @Override
+                public void run() {
+                    UUID offlineUpper = UUID.nameUUIDFromBytes(("OfflinePlayer:" + name.value).getBytes(Charsets.UTF_8));
+                    if (UUIDHandlerImplementation.this.unknown.contains(offlineUpper) && offlineUpper != null && !offlineUpper.equals(uuid)) {
+                        UUIDHandlerImplementation.this.unknown.remove(offlineUpper);
+                        Set<Plot> plots = PS.get().getPlotsAbs(offlineUpper);
+                        if (!plots.isEmpty()) {
+                            for (Plot plot : plots) {
+                                plot.owner = uuid;
+                            }
+                            DBFunc.replaceUUID(offlineUpper, uuid);
+                            PS.debug("&cDetected invalid UUID stored for: " + name.value);
+                            PS.debug("&7 - Did you recently switch to online-mode storage without running `uuidconvert`?");
+                            PS.debug("&6PlotSquared will update incorrect entries when the user logs in, or you can reconstruct your database.");
+                        }
+                    }
+                }
+            });
         }
         try {
             UUID offline = this.uuidMap.put(name, uuid);