diff --git a/src/classes/PRunAsymmetry.cpp b/src/classes/PRunAsymmetry.cpp
index c72133d4..e72ec4de 100644
--- a/src/classes/PRunAsymmetry.cpp
+++ b/src/classes/PRunAsymmetry.cpp
@@ -549,6 +549,9 @@ void PRunAsymmetry::CalcTheory()
  */
 Bool_t PRunAsymmetry::PrepareData()
 {
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/classes/PRunAsymmetryBNMR.cpp b/src/classes/PRunAsymmetryBNMR.cpp
index 25c16101..b1e34697 100644
--- a/src/classes/PRunAsymmetryBNMR.cpp
+++ b/src/classes/PRunAsymmetryBNMR.cpp
@@ -587,6 +587,9 @@ void PRunAsymmetryBNMR::CalcTheory()
  */
 Bool_t PRunAsymmetryBNMR::PrepareData()
 {
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/classes/PRunAsymmetryRRF.cpp b/src/classes/PRunAsymmetryRRF.cpp
index 1fb478be..4036c652 100644
--- a/src/classes/PRunAsymmetryRRF.cpp
+++ b/src/classes/PRunAsymmetryRRF.cpp
@@ -531,6 +531,9 @@ void PRunAsymmetryRRF::CalcTheory()
  */
 Bool_t PRunAsymmetryRRF::PrepareData()
 {
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/classes/PRunDataHandler.cpp b/src/classes/PRunDataHandler.cpp
index c0503e0f..fcc3975b 100644
--- a/src/classes/PRunDataHandler.cpp
+++ b/src/classes/PRunDataHandler.cpp
@@ -436,6 +436,8 @@ Bool_t PRunDataHandler::ReadFilesMsr()
         success = ReadAsciiFile();
       } else if (!runList->at(i).GetFileFormat(j)->CompareTo("db")) {
         success = ReadDBFile();
+      } else if (!runList->at(i).GetFileFormat(j)->CompareTo("dat")) {
+        success = ReadDatFile();
       } else {
         success = false;
       }
@@ -994,6 +996,8 @@ Bool_t PRunDataHandler::FileExistsCheck(PMsrRunBlock &runInfo, const UInt_t idx)
     ext = TString("dat");
   else if (!runInfo.GetFileFormat(idx)->CompareTo("db"))
     ext = TString("db");
+  else if (!runInfo.GetFileFormat(idx)->CompareTo("dat"))
+    ext = TString("dat");
   else
     success = false;
 
@@ -1018,6 +1022,7 @@ Bool_t PRunDataHandler::FileExistsCheck(PMsrRunBlock &runInfo, const UInt_t idx)
     std::cerr << std::endl << ">>   MDU-ASCII  -> psi mdu ascii file format";
     std::cerr << std::endl << ">>   ASCII      -> column like file format";
     std::cerr << std::endl << ">>   DB         -> triumf db file \"format\"";
+    std::cerr << std::endl << ">>   DAT        -> csv like file \"format\" as exported by msr2data.";
     std::cerr << std::endl;
     return success;
   }
@@ -4238,6 +4243,18 @@ Bool_t PRunDataHandler::ReadDBFile()
   return success;
 }
 
+//--------------------------------------------------------------------------
+// ReadDBFile (private)
+//--------------------------------------------------------------------------
+Bool_t PRunDataHandler::ReadDatFile()
+{
+  Bool_t success = true;
+
+  std::cerr << "debug> in PRunDataHandler::ReadDatFile(). Not yet implemented..." << std::endl;
+
+  return success;
+}
+
 //--------------------------------------------------------------------------
 // WriteMusrRootFile (private)
 //--------------------------------------------------------------------------
diff --git a/src/classes/PRunMuMinus.cpp b/src/classes/PRunMuMinus.cpp
index 07d00cf6..ef7c6326 100644
--- a/src/classes/PRunMuMinus.cpp
+++ b/src/classes/PRunMuMinus.cpp
@@ -458,6 +458,9 @@ Bool_t PRunMuMinus::PrepareData()
 {
   Bool_t success = true;
 
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/classes/PRunNonMusr.cpp b/src/classes/PRunNonMusr.cpp
index d078ed38..1e063c7e 100644
--- a/src/classes/PRunNonMusr.cpp
+++ b/src/classes/PRunNonMusr.cpp
@@ -198,6 +198,9 @@ Bool_t PRunNonMusr::PrepareData()
 {
   Bool_t success = true;
 
+  if (!fValid)
+    return false;
+
   if (fRunInfo->GetRunNameSize() > 1) { // ADDRUN present which is not supported for NonMusr
     std::cerr << std::endl << ">> PRunNonMusr::PrepareData(): **WARNING** ADDRUN NOT SUPPORTED FOR THIS FIT TYPE, WILL IGNORE IT." << std::endl;
   }
diff --git a/src/classes/PRunSingleHisto.cpp b/src/classes/PRunSingleHisto.cpp
index f0c4c6a8..ff453390 100644
--- a/src/classes/PRunSingleHisto.cpp
+++ b/src/classes/PRunSingleHisto.cpp
@@ -700,6 +700,9 @@ Bool_t PRunSingleHisto::PrepareData()
 {
   Bool_t success = true;
 
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/classes/PRunSingleHistoRRF.cpp b/src/classes/PRunSingleHistoRRF.cpp
index 00904b82..ac34cf36 100644
--- a/src/classes/PRunSingleHistoRRF.cpp
+++ b/src/classes/PRunSingleHistoRRF.cpp
@@ -431,6 +431,9 @@ Bool_t PRunSingleHistoRRF::PrepareData()
 {
   Bool_t success = true;
 
+  if (!fValid)
+    return false;
+
   // keep the Global block info
   PMsrGlobalBlock *globalBlock = fMsrInfo->GetMsrGlobal();
 
diff --git a/src/include/PRunDataHandler.h b/src/include/PRunDataHandler.h
index 16ef4657..4fff51f5 100644
--- a/src/include/PRunDataHandler.h
+++ b/src/include/PRunDataHandler.h
@@ -87,6 +87,7 @@ class PRunDataHandler
     virtual Bool_t ReadMduAsciiFile();
     virtual Bool_t ReadAsciiFile();
     virtual Bool_t ReadDBFile();
+    virtual Bool_t ReadDatFile();
 
     virtual Bool_t WriteMusrRootFile(TString fln="");
     virtual Bool_t WriteRootFile(TString fln="");