diff --git a/code/sample/itape.py b/code/sample/itape.py
index eb6d1b3..994dd4f 100755
--- a/code/sample/itape.py
+++ b/code/sample/itape.py
@@ -37,7 +37,7 @@ beta1     5
 hrp       0.75
 le_a      1.
 le_x      0.20
-nsp       1
+nsp       2
 nrxn      1
 '''
 ).split()
diff --git a/code/ysolve.f90 b/code/ysolve.f90
index 887a1e9..6fb348a 100644
--- a/code/ysolve.f90
+++ b/code/ysolve.f90
@@ -115,7 +115,14 @@
 
        CALL SET_BC
 
-       CALL RK4(fns)
+       if ( reaction_type == "onestep" ) then
+         CALL RK4(fonestep)
+       else if ( reaction_type == "twostep" ) then
+         CALL RK4(fns)
+       else
+           WRITE(*,*) 'ERROR, UNDEFINED REACTION TYPE ', reaction_type
+           stop
+       end if
 
        IF (t_uf.ge.dt_uf) THEN
          pflold=pflame
@@ -240,7 +247,7 @@
 
       OPEN (305,FILE='sfield.dat')
       DO i=1,nx
-       WRITE (305,'(4e30.20)') i*hx, y1(i,1), y1(i,2), y1(i,3)
+       WRITE (305,*) (/ i*hx, y1(i,:) /)
       ENDDO
       CLOSE (305)
 
@@ -343,6 +350,8 @@
          xi = x(i)
 
          y1(i,1)=(1.-xi)   ! reactant mass fraction
+         y1(i,2)=(xi)   ! reactant mass fraction
+
         ENDDO
       else if ( reaction_type == "twostep" ) then
         DO i=1,nx