diff --git a/ChangeLog b/ChangeLog
index 7173bbc1..e2aef541 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,6 +20,7 @@ NEW 2012-04-24 added a first version for negative muon fitting. At the same
 	       logx/logy handling).
 FIXED 2012-05-30 fixed RRF  bug in single histo plotting.
 FIXED 2012-05-18 fixed wrong forward/backward tag for ROOT-PPC (MUSR-215) 
+CHANGED 2012-08-28 prevent LF from allocating too much memory
 CHANGED 2012-06-29 changed handling of the timeout for musrfit.
 CHANGED 2012-05-10 prevent any2many from overwriting an input file. At the
    some additional bug fixing of any2many has be carried out.
diff --git a/src/classes/PTheory.cpp b/src/classes/PTheory.cpp
index 97f2f4c8..27664ad7 100644
--- a/src/classes/PTheory.cpp
+++ b/src/classes/PTheory.cpp
@@ -2595,10 +2595,10 @@ void PTheory::CalculateDynKTLF(const Double_t *val, Int_t tag) const
     Double_t tmin = 20.0;
     switch (tag) {
       case 0: // Gauss
-        tmin = sqrt(3.0)/val[1];
+        tmin = fabs(sqrt(3.0)/val[1]);
         break;
       case 1: // Lorentz
-        tmin = 2.0/val[1];
+        tmin = fabs(2.0/val[1]);
         break;
       default:
         break;
@@ -2612,6 +2612,9 @@ void PTheory::CalculateDynKTLF(const Double_t *val, Int_t tag) const
   if (N < 300) // if too few points, i.e. nu0 very small, take 300 points
     N = 300;
 
+  if (N>1e6) // make sure that N is not too large to prevent memory overflow
+    N = 1e6;
+
   // allocate memory for dyn KT LF function vector
   fDynLFFuncValue.clear(); // get rid of a possible previous vector
   fDynLFFuncValue.resize(N);