diff --git a/src/musrFT.cpp b/src/musrFT.cpp
index a9bf6ca1..ee2616e1 100644
--- a/src/musrFT.cpp
+++ b/src/musrFT.cpp
@@ -1075,6 +1075,21 @@ Int_t main(Int_t argc, Char_t *argv[])
     }
   }
 
+  // check for ascii-, db- or dat-files in msr-file RUN block
+  TString ffstr("");
+  for (UInt_t i=0; i<msrHandler.size(); i++) {
+    PMsrRunList *runList = msrHandler[i]->GetMsrRunList();
+    for (UInt_t j=0; j<runList->at(i).GetFileFormatSize(); j++) {
+      ffstr = *(runList->at(i).GetFileFormat(j));
+      if (!ffstr.CompareTo("ascii", TString::kIgnoreCase) || !ffstr.CompareTo("dat", TString::kIgnoreCase) || !ffstr.CompareTo("db", TString::kIgnoreCase)) {
+        std::cout << std::endl;
+        std::cout << "**ERROR** Currently file format's 'ASCII', 'DAT', nor 'DB' are NOT supported." << std::endl;
+        std::cout << std::endl;
+        return PMUSR_UNSUPPORTED_FEATURE;
+      }
+    }
+  }
+
   std::vector< std::unique_ptr<PRunDataHandler> > runDataHandler;
   runDataHandler.resize(startupParam.msrFln.size()+startupParam.dataFln.size()); // resize to the total number of run data provided
   // load data-file(s) related to msr-file