diff --git a/src/io.c b/src/io.c
index 049f310..94816f9 100644
--- a/src/io.c
+++ b/src/io.c
@@ -14,7 +14,7 @@ int write_u(_Complex double* u, int K1, int K2, FILE* file){
 
   for(kx=0;kx<=K1;kx++){
     for (ky=-K2;ky<=K2;ky++){
-      fprintf(file,"%d %d % .15e % .15e\n",kx,ky,__real__ u[klookup_sym(kx,ky,K2)],__imag__ u[klookup_sym(kx,ky,K2)]);
+      fprintf(file,"% 3d % 3d % .15e % .15e\n",kx,ky,__real__ u[klookup_sym(kx,ky,K2)],__imag__ u[klookup_sym(kx,ky,K2)]);
     }
   }