diff --git a/src/usher-sampled/driver/main.cpp b/src/usher-sampled/driver/main.cpp
index b6a42d49..4063d907 100644
--- a/src/usher-sampled/driver/main.cpp
+++ b/src/usher-sampled/driver/main.cpp
@@ -429,6 +429,7 @@ int main(int argc, char **argv) {
     if (options.initial_optimization_radius<=0) {
         options.parsimony_threshold=INT_MAX;
     }
+    num_threads=std::max(2u,num_threads);
     options.desired_optimization_msec=optimiation_minutes*60000;
     fprintf(stderr, "Num threads %d\n",num_threads);
 #ifdef __linux
diff --git a/src/usher-sampled/driver/socket.cpp b/src/usher-sampled/driver/socket.cpp
index 6c31269c..bd3b7552 100644
--- a/src/usher-sampled/driver/socket.cpp
+++ b/src/usher-sampled/driver/socket.cpp
@@ -18,6 +18,7 @@
 #include <fstream>
 #include <functional>
 #include <iomanip>
+#include <ios>
 #include <iostream>
 #include <memory>
 #include <mutex>
@@ -399,7 +400,7 @@ static void child_proc(int fd, TreeCollectionPtr &trees_ptr) {
     tbb::task_scheduler_init init(num_threads);
     if (existing_samples != "") {
         MAT::Tree &tree = iter->second->expanded_tree;
-        std::fstream sample_file(existing_samples);
+        std::fstream sample_file(existing_samples,std::ios_base::in);
         std::string sample_name;
         std::vector<MAT::Node *> nodes_to_extract;
         while (sample_file) {