diff --git a/wwpdb/utils/nmr/NmrDpUtility.py b/wwpdb/utils/nmr/NmrDpUtility.py
index 029719ab..8c847b1b 100644
--- a/wwpdb/utils/nmr/NmrDpUtility.py
+++ b/wwpdb/utils/nmr/NmrDpUtility.py
@@ -8111,7 +8111,6 @@ def __validateInputSource(self, srcPath: str = None) -> bool:
                     csPath = _csPath
 
                 if self.__op == 'nmr-cs-mr-merge' and not os.path.basename(csPath).startswith('bmr'):
-
                     _csPath = csPath + '.cif2str'
 
                     if not self.__c2S.convert(csPath, _csPath):
@@ -8657,6 +8656,11 @@ def __fixFormatIssueOfInputSource(self, file_list_id: int, file_name: str, file_
                 _srcPath = ofh.name
                 tmpPaths.append(_srcPath)
 
+            # fix single loop file without datablock (D_1300055931)
+            if self.__c2S.convert(_srcPath, _srcPath + '~'):
+                _srcPath = _srcPath + '~'
+                tmpPaths.append(_srcPath)
+
         msg_template = "Only 'save_NAME' is valid in the body of a NMR-STAR file. Found 'loop_'."
 
         if any(msg for msg in message['error'] if msg_template in msg):