diff --git a/src/DockerRunner.jl b/src/DockerRunner.jl
index 3488cd5d..5ce37fc3 100644
--- a/src/DockerRunner.jl
+++ b/src/DockerRunner.jl
@@ -212,7 +212,21 @@ function run_interactive(dr::DockerRunner, cmd::Cmd; stdin = nothing, stdout = n
 
     try
         mount_shards(dr; verbose=verbose)
-        return success(run(docker_cmd))
+        if stdout isa IOBuffer
+            if !(stdin isa IOBuffer)
+                stdin = devnull
+            end
+            process = open(docker_cmd, "r", stdin)
+            @async begin
+                while !eof(process)
+                    write(stdout, read(process))
+                end
+            end
+            wait(process)
+            return success(process)
+        else
+            return success(run(docker_cmd))
+        end
     finally
         unmount_shards(dr; verbose=verbose)
         # Cleanup permissions, if we need to.
diff --git a/src/UserNSRunner.jl b/src/UserNSRunner.jl
index bffb9061..3ea57f44 100644
--- a/src/UserNSRunner.jl
+++ b/src/UserNSRunner.jl
@@ -62,7 +62,7 @@ function UserNSRunner(workspace_root::String;
         sandbox_cmd = `$sandbox_cmd --verbose`
     end
     sandbox_cmd = `$sandbox_cmd --rootfs $(mpath)`
-    if cwd !== nothing
+    if cwd != nothing
         sandbox_cmd = `$sandbox_cmd --cd $cwd`
     end
 
@@ -204,7 +204,21 @@ function run_interactive(ur::UserNSRunner, user_cmd::Cmd; stdin = nothing, stdou
 
     try
         mount_shards(ur; verbose=verbose)
-        return success(run(cmd))
+        if stdout isa IOBuffer
+            if !(stdin isa IOBuffer)
+                stdin = devnull
+            end
+            process = open(cmd, "r", stdin)
+            @async begin
+                while !eof(process)
+                    write(stdout, read(process))
+                end
+            end
+            wait(process)
+            return success(process)
+        else
+            return success(run(cmd))
+        end
     finally
         unmount_shards(ur)
     end