diff --git a/SRC/BPACK_defs.f90 b/SRC/BPACK_defs.f90
index 91e8fd6..53523ae 100755
--- a/SRC/BPACK_defs.f90
+++ b/SRC/BPACK_defs.f90
@@ -642,7 +642,7 @@ module BPACK_DEFS
         ! options for inversion
         real(kind=8) tol_LS       !< tolerance in pseudo inverse
         real(kind=8) tol_Rdetect  !< tolerance to detect numerical ranks
-        real(kind=8) tol_rand     !< tolerance for randomized contruction
+        real(kind=8) tol_rand     !< tolerance for randomized contruction, mostly used in matrix inversion
         real(kind=8) jitter     !< jittering for dense diagonal blocks
         integer powiter     !< order of power iteration in randomized LR
         integer less_adapt     !< 0 for rank adaptation for all BF levels, 1 for rank adaptation for the outtermost BF levels
diff --git a/SRC/BPACK_solve_mul.f90 b/SRC/BPACK_solve_mul.f90
index c5c1637..02775f4 100755
--- a/SRC/BPACK_solve_mul.f90
+++ b/SRC/BPACK_solve_mul.f90
@@ -1024,6 +1024,14 @@ subroutine BPACK_Ztfqmr(precond, ntotal, nn_loc, b, x, err, iter, r0_initial, bm
          we_local = dot_product(w, w)
          call MPI_ALLREDUCE(we_local, we_sum, 1, MPI_DT, MPI_SUM, &
                             ptree%Comm, ierr)
+         if (ta<=1d-30) then
+            if (ptree%MyID == Main_ID) print *, 'Warning: TFQMR halts, returning now.'
+            err = rerr
+            iter = it
+            return
+            ! write(32,*)'# ofiter,error:',it,rerr ! iterations file
+         end if
+
          we = sqrt(abs(we_sum))/ta
          cm = 1.0d0/sqrt(1.0d0 + we*we)
          ta = ta*we*cm