diff --git a/lib/Controller/FileHandlingController.php b/lib/Controller/FileHandlingController.php
index 43d601fd..6ea3c6f3 100644
--- a/lib/Controller/FileHandlingController.php
+++ b/lib/Controller/FileHandlingController.php
@@ -136,6 +136,10 @@ public function save($path, $filecontents, $mtime) {
 				}
 			
 				if($file->isUpdateable()) {
+					if (empty($mtime)) {
+						$this->logger->error('Save request without the modification time of the loaded file: ' . $path, ['app' => 'files_mindmap']);
+						return new DataResponse(['message' => $this->l->t('The mind map could not be saved. Please reload it and try again.')], Http::STATUS_BAD_REQUEST);
+					}
 					if ($mtime != $file->getMTime()) {
 						$this->logger->error("User cannot save shared mind map (someone updated it in the meantime): {$mtime} vs. {$file->getMTime()} {$file->getPath()}", ['app' => 'files_mindmap']);
 						return new DataResponse([ 'message' => $this->l->t('The file you are working on was updated in the meantime. You cannot save your progress as saving would overwrite these changes. Please reload the page.')],Http::STATUS_BAD_REQUEST);
@@ -159,24 +163,21 @@ public function save($path, $filecontents, $mtime) {
 				} else {
 					// Not writeable!
 					$this->logger->error('User does not have permission to write to file: ' . $path,
-						['app' => 'files_texteditor']);
+						['app' => 'files_mindmap']);
 					return new DataResponse([ 'message' => $this->l->t('Insufficient permissions')],
 						Http::STATUS_BAD_REQUEST);
 				}
-			} else if ($path === '') {
+			} else {
 				$this->logger->error('No file path supplied');
 				return new DataResponse(['message' => $this->l->t('File path not supplied')], Http::STATUS_BAD_REQUEST);
-			} else {
-				$this->logger->error('No file mtime supplied', ['app' => 'files_texteditor']);
-				return new DataResponse(['message' => $this->l->t('File mtime not supplied')], Http::STATUS_BAD_REQUEST);
 			}
 
 		} catch (HintException $e) {
 			$message = (string)$e->getHint();
 			return new DataResponse(['message' => $message], Http::STATUS_BAD_REQUEST);
 		} catch (\Exception $e) {
-			$message = (string)$this->l->t('An internal server error occurred.');
-			$message = $path;
+			$this->logger->error('Could not save mind map: ' . $path, ['app' => 'files_mindmap', 'exception' => $e]);
+			$message = (string)$this->l->t('The mind map could not be saved. Please try again later.');
 			return new DataResponse(['message' => $message], Http::STATUS_BAD_REQUEST);
 		}
 	}
diff --git a/lib/Controller/PublicFileHandlingController.php b/lib/Controller/PublicFileHandlingController.php
index d575efcb..0b64ce2e 100644
--- a/lib/Controller/PublicFileHandlingController.php
+++ b/lib/Controller/PublicFileHandlingController.php
@@ -207,6 +207,10 @@ public function save($token, $filecontents, $path, $mtime) {
         }
 
         if(($file instanceof File) && $file->isUpdateable()) {
+            if (empty($mtime)) {
+                $this->logger->error('Save request without the modification time of the loaded file: ' . $file->getPath(), ['app' => 'files_mindmap']);
+                return new DataResponse(['message' => $this->l->t('The mind map could not be saved. Please reload it and try again.')], Http::STATUS_BAD_REQUEST);
+            }
             if ($mtime != $file->getMTime()) {
                 $this->logger->error("Anonymous cannot save shared mind map (someone updated it in the meantime): {$mtime} vs. {$file->getMTime()} {$file->getPath()}", ['app' => 'files_mindmap']);
                 return new DataResponse([ 'message' => $this->l->t('The file you are working on was updated in the meantime. You cannot save your progress as saving would overwrite these changes. Please reload the page.')],Http::STATUS_BAD_REQUEST);