diff --git a/src/dump.cpp b/src/dump.cpp
index b04a9bf413..51dae8b131 100644
--- a/src/dump.cpp
+++ b/src/dump.cpp
@@ -1067,14 +1067,15 @@ void Dump::modify_params(int narg, char **arg)
       if (strstr(arg[iarg+1],"v_") == arg[iarg+1]) {
         delete[] output->var_dump[idump];
         output->var_dump[idump] = utils::strdup(&arg[iarg+1][2]);
+        output->last_dump[idump] = -1;
         n = 0;
       } else {
         n = utils::inumeric(FLERR,arg[iarg+1],false,lmp);
         if (n <= 0) error->all(FLERR, "Invalid dump_modify every argument: {}", n);
+        output->next_dump[idump] = (update->ntimestep/n)*n+n;
       }
       output->mode_dump[idump] = 0;
       output->every_dump[idump] = n;
-      output->next_dump[idump] = (update->ntimestep/n)*n+n;
       iarg += 2;
 
     } else if (strcmp(arg[iarg],"every/time") == 0) {