diff --git a/src/integration-test/kotlin/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTextureManagerTest.kt b/src/integration-test/kotlin/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTextureManagerTest.kt
new file mode 100644
index 000000000..778fa459b
--- /dev/null
+++ b/src/integration-test/kotlin/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTextureManagerTest.kt
@@ -0,0 +1,93 @@
+/*
+ * Minosoft
+ * Copyright (C) 2020-2023 Moritz Zwerger
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * This software is not affiliated with Mojang AB, the original developer of Minecraft.
+ */
+
+package de.bixilon.minosoft.gui.rendering.gui.atlas.textures
+
+import de.bixilon.kotlinglm.vec2.Vec2i
+import de.bixilon.minosoft.gui.rendering.RenderContext
+import de.bixilon.minosoft.gui.rendering.system.base.texture.data.TextureData
+import de.bixilon.minosoft.gui.rendering.system.base.texture.texture.memory.TextureGenerator
+import de.bixilon.minosoft.test.IT
+import org.testng.Assert.assertEquals
+import org.testng.annotations.Test
+
+@Test(groups = ["atlas", "gui"])
+class AtlasTextureManagerTest {
+
+    private fun create(): AtlasTextureManager {
+        val context = IT.OBJENESIS.newInstance(RenderContext::class.java)
+
+        return AtlasTextureManager(context)
+    }
+
+    fun construct() {
+        create()
+    }
+
+    private fun createTexture(size: Vec2i): TextureData {
+        val data = TextureData(size, TextureGenerator.allocate(size))
+        for (index in 0 until data.buffer.limit()) {
+            data.buffer.put(0xFF.toByte())
+        }
+
+        for (y in 0 until size.y) {
+            for (x in 0 until size.x) {
+                val offset = ((size.x * y) + x) * 4
+                data.buffer.put(offset, (x + 1).toByte())
+            }
+        }
+
+        return data
+    }
+
+    private fun AtlasTexture.getR(x: Int, y: Int): Int {
+        val offset = ((y * size.x) + x) * 4
+        return data.buffer[offset].toInt() and 0xFF
+    }
+
+    fun `copy simple texture to atlas texture`() {
+        val texture = AtlasTexture(Vec2i(16, 16))
+        val source = createTexture(Vec2i(4, 4))
+        texture.put(Vec2i(1, 1), source, Vec2i(1, 1), Vec2i(3, 3))
+
+        assertEquals(texture.getR(0, 0), 0x00)
+        assertEquals(texture.getR(1, 0), 0x00)
+        assertEquals(texture.getR(2, 0), 0x00)
+        assertEquals(texture.getR(3, 0), 0x00)
+        assertEquals(texture.getR(4, 0), 0x00)
+
+        assertEquals(texture.getR(0, 1), 0x00)
+        assertEquals(texture.getR(1, 1), 0x02)
+        assertEquals(texture.getR(2, 1), 0x03)
+        assertEquals(texture.getR(3, 1), 0x04)
+        assertEquals(texture.getR(4, 1), 0x00)
+
+        assertEquals(texture.getR(0, 2), 0x00)
+        assertEquals(texture.getR(1, 2), 0x02)
+        assertEquals(texture.getR(2, 2), 0x03)
+        assertEquals(texture.getR(3, 2), 0x04)
+        assertEquals(texture.getR(4, 2), 0x00)
+
+        assertEquals(texture.getR(0, 3), 0x00)
+        assertEquals(texture.getR(1, 3), 0x02)
+        assertEquals(texture.getR(2, 3), 0x03)
+        assertEquals(texture.getR(3, 3), 0x04)
+        assertEquals(texture.getR(4, 3), 0x00)
+
+        assertEquals(texture.getR(0, 4), 0x00)
+        assertEquals(texture.getR(1, 4), 0x00)
+        assertEquals(texture.getR(2, 4), 0x00)
+        assertEquals(texture.getR(3, 4), 0x00)
+        assertEquals(texture.getR(4, 4), 0x00)
+    }
+}
diff --git a/src/main/java/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTexture.kt b/src/main/java/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTexture.kt
index 986bf47ff..5b9aaea1b 100644
--- a/src/main/java/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTexture.kt
+++ b/src/main/java/de/bixilon/minosoft/gui/rendering/gui/atlas/textures/AtlasTexture.kt
@@ -42,8 +42,8 @@ class AtlasTexture(
     fun request(size: Vec2i): Vec2i? = null
 
     fun put(offset: Vec2i, source: TextureData, start: Vec2i, size: Vec2i): CodeTexturePart {
-        for (x in 0 until size.x) {
-            for (y in 0 until size.y) {
+        for (y in 0 until size.y) {
+            for (x in 0 until size.x) {
                 val sourceOffset = ((start.y + y) * source.size.x + (start.x + x)) * 4
                 val destinationOffset = ((offset.y + y) * this.size.x + (offset.x + x)) * 4