diff --git a/exp/audio/audio.go b/exp/audio/audio.go
index 372db1d4e..3d3e903db 100644
--- a/exp/audio/audio.go
+++ b/exp/audio/audio.go
@@ -15,7 +15,7 @@
 package audio
 
 import (
-	"github.com/hajimehoshi/ebiten/exp/audio/internal"
+	"github.com/hajimehoshi/ebiten/exp/audio/inner"
 )
 
 // SampleRate returns the sampling frequency (e.g. 44100).
diff --git a/exp/audio/internal/audio.go b/exp/audio/inner/audio.go
similarity index 100%
rename from exp/audio/internal/audio.go
rename to exp/audio/inner/audio.go
diff --git a/exp/audio/internal/audio_js.go b/exp/audio/inner/audio_js.go
similarity index 100%
rename from exp/audio/internal/audio_js.go
rename to exp/audio/inner/audio_js.go
diff --git a/exp/audio/internal/audio_openal.go b/exp/audio/inner/audio_openal.go
similarity index 100%
rename from exp/audio/internal/audio_openal.go
rename to exp/audio/inner/audio_openal.go
diff --git a/exp/audio/internal/audio_windows.go b/exp/audio/inner/audio_windows.go
similarity index 100%
rename from exp/audio/internal/audio_windows.go
rename to exp/audio/inner/audio_windows.go
diff --git a/gamecontext.go b/gamecontext.go
index f41ec1136..902545647 100644
--- a/gamecontext.go
+++ b/gamecontext.go
@@ -15,9 +15,9 @@
 package ebiten
 
 import (
-	audio "github.com/hajimehoshi/ebiten/exp/audio/internal"
+	audio "github.com/hajimehoshi/ebiten/exp/audio/inner"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"github.com/hajimehoshi/ebiten/internal/ui"
 	"image"
 )
diff --git a/graphics.go b/graphics.go
index 749eba307..731483456 100644
--- a/graphics.go
+++ b/graphics.go
@@ -15,7 +15,7 @@
 package ebiten
 
 import (
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 )
 
 // Filter represents the type of filter to be used when an image is maginified or minified.
diff --git a/graphicscontext.go b/graphicscontext.go
index 615824cd9..abe55d86f 100644
--- a/graphicscontext.go
+++ b/graphicscontext.go
@@ -16,7 +16,7 @@ package ebiten
 
 import (
 	"github.com/hajimehoshi/ebiten/internal/graphics"
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"github.com/hajimehoshi/ebiten/internal/ui"
 )
 
diff --git a/image.go b/image.go
index eaa9c1d00..8985f9ce9 100644
--- a/image.go
+++ b/image.go
@@ -18,7 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"image"
 	"image/color"
 )
diff --git a/internal/graphics/draw.go b/internal/graphics/draw.go
index ab60363a5..db9a16949 100644
--- a/internal/graphics/draw.go
+++ b/internal/graphics/draw.go
@@ -17,7 +17,7 @@ package graphics
 import (
 	"errors"
 	"fmt"
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 )
 
 func glMatrix(m *[4][4]float64) []float32 {
diff --git a/internal/graphics/framebuffer.go b/internal/graphics/framebuffer.go
index f1de5fb3a..7b3143575 100644
--- a/internal/graphics/framebuffer.go
+++ b/internal/graphics/framebuffer.go
@@ -15,7 +15,7 @@
 package graphics
 
 import (
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"image/color"
 	"math"
 )
diff --git a/internal/graphics/internal/opengl/context.go b/internal/graphics/opengl/context.go
similarity index 98%
rename from internal/graphics/internal/opengl/context.go
rename to internal/graphics/opengl/context.go
index d13e484b6..e95c6e1a1 100644
--- a/internal/graphics/internal/opengl/context.go
+++ b/internal/graphics/opengl/context.go
@@ -73,6 +73,12 @@ func (c *Context) init() {
 	gl.BlendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA)
 }
 
+func (c *Context) Check() {
+	if e := gl.GetError(); e != gl.NO_ERROR {
+		panic(fmt.Sprintf("check failed: %d", e))
+	}
+}
+
 func (c *Context) NewTexture(width, height int, pixels []uint8, filter Filter) (Texture, error) {
 	var t uint32
 	gl.GenTextures(1, &t)
diff --git a/internal/graphics/internal/opengl/context_js.go b/internal/graphics/opengl/context_js.go
similarity index 100%
rename from internal/graphics/internal/opengl/context_js.go
rename to internal/graphics/opengl/context_js.go
diff --git a/internal/graphics/internal/opengl/locationcache.go b/internal/graphics/opengl/locationcache.go
similarity index 100%
rename from internal/graphics/internal/opengl/locationcache.go
rename to internal/graphics/opengl/locationcache.go
diff --git a/internal/graphics/internal/opengl/types.go b/internal/graphics/opengl/types.go
similarity index 100%
rename from internal/graphics/internal/opengl/types.go
rename to internal/graphics/opengl/types.go
diff --git a/internal/graphics/program.go b/internal/graphics/program.go
index 402009354..39c24493f 100644
--- a/internal/graphics/program.go
+++ b/internal/graphics/program.go
@@ -15,7 +15,7 @@
 package graphics
 
 import (
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"math"
 )
 
diff --git a/internal/graphics/shader.go b/internal/graphics/shader.go
index 4c69ef2fb..a1002e7eb 100644
--- a/internal/graphics/shader.go
+++ b/internal/graphics/shader.go
@@ -15,7 +15,7 @@
 package graphics
 
 import (
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"strings"
 )
 
diff --git a/internal/graphics/texture.go b/internal/graphics/texture.go
index 98363cf1f..d6569c791 100644
--- a/internal/graphics/texture.go
+++ b/internal/graphics/texture.go
@@ -16,7 +16,7 @@ package graphics
 
 import (
 	"errors"
-	"github.com/hajimehoshi/ebiten/internal/graphics/internal/opengl"
+	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 	"image"
 	"image/draw"
 )
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index 877015284..b31863b3b 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -64,10 +64,16 @@ func Init() {
 
 func ExecOnUIThread(f func()) {
 	ch := make(chan struct{})
-	currentUI.funcs <- func() {
+	/*currentUI.funcs <- func() {
 		defer close(ch)
 		f()
-	}
+	}*/
+	go func() {
+		defer close(ch)
+		runtime.LockOSThread()
+		currentUI.window.MakeContextCurrent()
+		f()
+	}()
 	<-ch
 }
 
diff --git a/run.go b/run.go
index 774e4a539..cdf3e2928 100644
--- a/run.go
+++ b/run.go
@@ -15,7 +15,7 @@
 package ebiten
 
 import (
-	audio "github.com/hajimehoshi/ebiten/exp/audio/internal"
+	audio "github.com/hajimehoshi/ebiten/exp/audio/inner"
 	"github.com/hajimehoshi/ebiten/internal/ui"
 	"time"
 )
@@ -54,6 +54,10 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 	}
 	defer ui.Terminate()
 
+	ui.ExecOnUIThread(func() {
+		glContext.Check()
+	})
+
 	graphicsContext, err := newGraphicsContext(width, height, actualScale)
 	if err != nil {
 		return err