diff --git a/src/Platform/AbstractXApplication.cpp b/src/Platform/AbstractXApplication.cpp
index 5b7b8bc35..591b72dfe 100644
--- a/src/Platform/AbstractXApplication.cpp
+++ b/src/Platform/AbstractXApplication.cpp
@@ -113,9 +113,6 @@ int AbstractXApplication::exec() {
     /* Show window */
     XMapWindow(display, window);
 
-    /* Call viewportEvent for the first time */
-    viewportEvent(viewportSize);
-
     while(!(flags & Flag::Exit)) {
         XEvent event;
 
diff --git a/src/Platform/GlutApplication.h b/src/Platform/GlutApplication.h
index 228e05332..67169128c 100644
--- a/src/Platform/GlutApplication.h
+++ b/src/Platform/GlutApplication.h
@@ -144,6 +144,11 @@ class GlutApplication {
          * Called when window size changes. You should pass the new size to
          * DefaultFramebuffer::setViewport() and possibly elsewhere (cameras,
          * other framebuffers...).
+         *
+         * Note that this function might not get called at all if the window
+         * size doesn't change. You are responsible for configuring the initial
+         * state yourself, viewport of default framebuffer can be retrieved
+         * from @ref DefaultFramebuffer::viewport().
          */
         virtual void viewportEvent(const Vector2i& size) = 0;
 
diff --git a/src/Platform/NaClApplication.cpp b/src/Platform/NaClApplication.cpp
index dbbdaf0a2..c3a56a45e 100644
--- a/src/Platform/NaClApplication.cpp
+++ b/src/Platform/NaClApplication.cpp
@@ -109,9 +109,6 @@ bool NaClApplication::tryCreateContext(const Configuration& configuration) {
     RequestInputEvents(PP_INPUTEVENT_CLASS_MOUSE|PP_INPUTEVENT_CLASS_WHEEL);
     RequestFilteringInputEvents(PP_INPUTEVENT_CLASS_KEYBOARD);
 
-    /* Make sure viewportEvent() is called for first time */
-    flags |= Flag::ViewportUpdated;
-
     c = new Context;
     return true;
 }
@@ -164,14 +161,7 @@ void NaClApplication::DidChangeView(const pp::View& view) {
     /* Canvas resized */
     if(viewportSize != size) {
         graphics->ResizeBuffers(size.x(), size.y());
-        viewportSize = size;
-        flags |= Flag::ViewportUpdated;
-    }
-
-    /* Update viewport, if changed */
-    if(flags & Flag::ViewportUpdated) {
-        flags &= ~Flag::ViewportUpdated;
-        viewportEvent(size);
+        viewportEvent(viewportSize = size);
     }
 
     drawEvent();
diff --git a/src/Platform/NaClApplication.h b/src/Platform/NaClApplication.h
index 53d76ab07..d1de44e8c 100644
--- a/src/Platform/NaClApplication.h
+++ b/src/Platform/NaClApplication.h
@@ -261,12 +261,11 @@ class NaClApplication: public pp::Instance, public pp::Graphics3DClient, public
         struct ConsoleDebugOutput;
 
         enum class Flag: UnsignedByte {
-            ViewportUpdated = 1 << 0,
-            SwapInProgress = 1 << 1,
-            Redraw = 1 << 2,
-            FullscreenSwitchInProgress = 1 << 3,
-            WillBeFullscreen = 1 << 4,
-            MouseLocked = 1 << 5
+            SwapInProgress = 1 << 0,
+            Redraw = 1 << 1,
+            FullscreenSwitchInProgress = 1 << 2,
+            WillBeFullscreen = 1 << 3,
+            MouseLocked = 1 << 4
         };
         typedef Containers::EnumSet<Flag, UnsignedByte> Flags;