diff --git a/src/lyapunov.c b/src/lyapunov.c
index b496cf6..d2c48d3 100644
--- a/src/lyapunov.c
+++ b/src/lyapunov.c
@@ -214,6 +214,7 @@ int lyapunov_D_step(
 ){
   int lx,ly;
   double alpha;
+  int n;
 
   // compute fft of u for future use
   lyapunov_fft_u_T(u,K1,K2,N1,N2,fftu1,fftu2,fftu3,fftu4);
@@ -237,14 +238,15 @@ int lyapunov_D_step(
   // loop over columns
   for(lx=0;lx<=K1;lx++){
     for(ly=(lx>0 ? -K2 : 1);ly<=K2;ly++){
-
-      // do not use adaptive step algorithms for the tangent flow: it must be locked to the same times as u
-      if(algorithm==ALGORITHM_RK2){
-	lyapunov_D_step_rk2(flow+2*klookup_sym(lx,ly,K2)*MATSIZE, u, K1, K2, N1, N2, alpha, delta, L, g, tmp4, fftu1, fftu2, fftu3, fftu4, fft1, ifft, tmp1, tmp2, irreversible);
-      } else if (algorithm==ALGORITHM_RK4) {
-	lyapunov_D_step_rk4(flow+2*klookup_sym(lx,ly,K2)*MATSIZE, u, K1, K2, N1, N2, alpha, delta, L, g, tmp4, fftu1, fftu2, fftu3, fftu4, fft1, ifft, tmp1, tmp2, tmp3, irreversible);
-      } else {
-	fprintf(stderr,"bug: unknown algorithm for tangent flow: %u, contact ian.jauslin@rutgers.edu\n",algorithm);
+      for(n=0;n<=1;n++){
+	// do not use adaptive step algorithms for the tangent flow: it must be locked to the same times as u
+	if(algorithm==ALGORITHM_RK2){
+	  lyapunov_D_step_rk2(flow+(2*klookup_sym(lx,ly,K2)+n)*MATSIZE, u, K1, K2, N1, N2, alpha, delta, L, g, tmp4, fftu1, fftu2, fftu3, fftu4, fft1, ifft, tmp1, tmp2, irreversible);
+	} else if (algorithm==ALGORITHM_RK4) {
+	  lyapunov_D_step_rk4(flow+(2*klookup_sym(lx,ly,K2)+n)*MATSIZE, u, K1, K2, N1, N2, alpha, delta, L, g, tmp4, fftu1, fftu2, fftu3, fftu4, fft1, ifft, tmp1, tmp2, tmp3, irreversible);
+	} else {
+	  fprintf(stderr,"bug: unknown algorithm for tangent flow: %u, contact ian.jauslin@rutgers.edu\n",algorithm);
+	}
       }
     }
   }