diff --git a/src/anbox/cmds/session_manager.cpp b/src/anbox/cmds/session_manager.cpp
index a4d368d..d6ceac8 100644
--- a/src/anbox/cmds/session_manager.cpp
+++ b/src/anbox/cmds/session_manager.cpp
@@ -89,7 +89,8 @@ anbox::cmds::SessionManager::BusFactory anbox::cmds::SessionManager::session_bus
 anbox::cmds::SessionManager::SessionManager(const BusFactory &bus_factory)
     : CommandWithFlagsAndAction{cli::Name{"session-manager"}, cli::Usage{"session-manager"},
                                 cli::Description{"Run the the anbox session manager"}},
-      bus_factory_(bus_factory) {
+      bus_factory_(bus_factory),
+      window_size_(default_single_window_size) {
   // Just for the purpose to allow QtMir (or unity8) to find this on our
   // /proc/*/cmdline
   // for proper confinement etc.
@@ -102,6 +103,9 @@ anbox::cmds::SessionManager::SessionManager(const BusFactory &bus_factory)
   flag(cli::make_flag(cli::Name{"single-window"},
                       cli::Description{"Start in single window mode."},
                       single_window_));
+  flag(cli::make_flag(cli::Name{"window-size"},
+                      cli::Description{"Size of the window in single window mode, e.g. --window-size=1024,768"},
+                      window_size_));
 
   action([this](const cli::Command::Context &) {
     auto trap = core::posix::trap_signals_for_process(
@@ -143,7 +147,7 @@ anbox::cmds::SessionManager::SessionManager(const BusFactory &bus_factory)
 
     auto display_frame = graphics::Rect::Invalid;
     if (single_window_)
-      display_frame = default_single_window_size;
+      display_frame = window_size_;
 
     auto policy = std::make_shared<ubuntu::PlatformPolicy>(input_manager, display_frame, single_window_);
     // FIXME this needs to be removed and solved differently behind the scenes
diff --git a/src/anbox/cmds/session_manager.h b/src/anbox/cmds/session_manager.h
index e212f1d..9ffb419 100644
--- a/src/anbox/cmds/session_manager.h
+++ b/src/anbox/cmds/session_manager.h
@@ -27,6 +27,7 @@
 #include <core/dbus/bus.h>
 
 #include "anbox/graphics/gl_renderer_server.h"
+#include "anbox/graphics/rect.h"
 
 namespace anbox {
 namespace cmds {
@@ -43,6 +44,7 @@ class SessionManager : public cli::CommandWithFlagsAndAction {
   std::string desktop_file_hint_;
   graphics::GLRendererServer::Config::Driver gles_driver_;
   bool single_window_ = false;
+  graphics::Rect window_size_;
 };
 }  // namespace cmds
 }  // namespace anbox
diff --git a/src/anbox/graphics/rect.cpp b/src/anbox/graphics/rect.cpp
index b98116a..d3306c5 100644
--- a/src/anbox/graphics/rect.cpp
+++ b/src/anbox/graphics/rect.cpp
@@ -16,10 +16,13 @@
  */
 
 #include "anbox/graphics/rect.h"
+#include "anbox/utils.h"
 
 #include <algorithm>
 #include <string>
 
+#include <boost/lexical_cast.hpp>
+
 namespace anbox {
 namespace graphics {
 const Rect Rect::Invalid{-1, -1, -1, -1};
@@ -51,5 +54,34 @@ std::ostream &operator<<(std::ostream &out, const Rect &rect) {
              << "," << rect.bottom() << "} {" << rect.width() << ","
              << rect.height() << "}";
 }
+
+std::istream& operator>>(std::istream& in, anbox::graphics::Rect &rect)
+try {
+  std::string str;
+  in >> str;
+  auto tokens = anbox::utils::string_split(str, ',');
+
+  switch (tokens.size()) {
+  case 2: {
+    rect = anbox::graphics::Rect(0, 0,
+             boost::lexical_cast<std::int32_t>(tokens[0]),
+             boost::lexical_cast<std::int32_t>(tokens[1]));
+    break;
+  }
+  case 4:
+    rect = anbox::graphics::Rect(
+             boost::lexical_cast<std::int32_t>(tokens[0]),
+             boost::lexical_cast<std::int32_t>(tokens[1]),
+             boost::lexical_cast<std::int32_t>(tokens[2]),
+             boost::lexical_cast<std::int32_t>(tokens[3]));
+    break;
+  default:
+    break;
+  }
+
+  return in;
+} catch (...) {
+  return in;
+}
 }  // namespace graphics
 }  // namespace anbox
diff --git a/src/anbox/graphics/rect.h b/src/anbox/graphics/rect.h
index 8c3060e..3903727 100644
--- a/src/anbox/graphics/rect.h
+++ b/src/anbox/graphics/rect.h
@@ -75,6 +75,7 @@ class Rect {
 };
 
 std::ostream &operator<<(std::ostream &out, const Rect &rect);
+std::istream& operator>>(std::istream& in, anbox::graphics::Rect &rect);
 }  // namespace graphics
 }  // namespace anbox