Index: applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetTask.java
===================================================================
--- applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetTask.java	(revision 35868)
+++ applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetTask.java	(revision 35869)
@@ -98,9 +98,9 @@
                 newLayer = false; // reuse layer for subsequent reverts
             } catch (OsmTransferException e) {
-            	rollback(allcmds);
+                rollback(allcmds);
                 Logging.error(e);
                 throw e;
             } catch (UserCancelException e) {
-            	rollback(allcmds);
+                rollback(allcmds);
                 GuiHelper.executeByMainWorkerInEDT(() -> new Notification(tr("Revert was canceled")).show());
                 Logging.trace(e);
@@ -140,5 +140,5 @@
         if (progressMonitor.isCanceled())
             throw new UserCancelException();
-
+        int numOldConflicts = oldDataSet == null ? 0 : oldDataSet.getConflicts().size();
         // Check missing objects
         rev.checkMissingCreated();
@@ -154,4 +154,11 @@
             rev.downloadMissingPrimitives(progressMonitor.createSubTaskMonitor(ProgressMonitor.ALL_TICKS, false));
         }
+        int numConflicts = oldDataSet == null ? 0 : oldDataSet.getConflicts().size();
+        if (numConflicts > numOldConflicts) {
+            GuiHelper.runInEDT(() -> new Notification(tr("Please solve conflicts and maybe try again to revert."))
+            .setIcon(JOptionPane.ERROR_MESSAGE)
+            .show());
+            return null;
+        }
 
         if (progressMonitor.isCanceled())
@@ -173,10 +180,10 @@
         }
         GuiHelper.runInEDT(() -> {
-        	for (Command c : cmds) {
-        		if (c instanceof ConflictAddCommand) {
-        			numberOfConflicts++;
-        		}
-        		c.executeCommand();
-        	}
+            for (Command c : cmds) {
+                if (c instanceof ConflictAddCommand) {
+                    numberOfConflicts++;
+                }
+                c.executeCommand();
+            }
         });
         final String desc;
@@ -189,14 +196,14 @@
     }
 
-	@Override
-	protected void cancel() {
+    @Override
+    protected void cancel() {
         // nothing to do
-	}
-
-	@Override
-	protected void finish() {
+    }
+
+    @Override
+    protected void finish() {
         // nothing to do
 
-	}
+    }
 
     /**