diff --git a/IO/src/GLDefines.h b/IO/src/GLDefines.h
index 26b9d68..e22fc92 100644
--- a/IO/src/GLDefines.h
+++ b/IO/src/GLDefines.h
@@ -59,20 +59,34 @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
-#ifndef COMPRESSED_RGB_PVRTC_4BPPV1_IMG
-#define COMPRESSED_RGB_PVRTC_4BPPV1_IMG 0x8C00
+#ifndef GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG
+#define GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG 0x8C00
 #endif
 
-#ifndef COMPRESSED_RGB_PVRTC_2BPPV1_IMG
-#define COMPRESSED_RGB_PVRTC_2BPPV1_IMG 0x8C01
+#ifndef GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG
+#define GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG 0x8C01
 #endif
 
-#ifndef COMPRESSED_RGBA_PVRTC_4BPPV1_IMG
-#define COMPRESSED_RGBA_PVRTC_4BPPV1_IMG 0x8C02
+#ifndef GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG
+#define GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG 0x8C02
 #endif
 
-#ifndef COMPRESSED_RGBA_PVRTC_2BPPV1_IMG
-#define COMPRESSED_RGBA_PVRTC_2BPPV1_IMG 0x8C03
+#ifndef GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG
+#define GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG 0x8C03
+#endif
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// DXT definitions
+//
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef GL_COMPRESSED_RGB_S3TC_DXT1_EXT
+#define GL_COMPRESSED_RGB_S3TC_DXT1_EXT 0x83F0
+#endif
+
+#ifndef GL_COMPRESSED_RGBA_S3TC_DXT5_EXT
+#define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -81,60 +95,60 @@
 //
 ////////////////////////////////////////////////////////////////////////////////
 
-#ifndef COMPRESSED_RGBA_ASTC_4x4_KHR
-#define COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0
+#ifndef GL_COMPRESSED_RGBA_ASTC_4x4_KHR
+#define GL_COMPRESSED_RGBA_ASTC_4x4_KHR 0x93B0
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_5x4_KHR
-#define COMPRESSED_RGBA_ASTC_5x4_KHR 0x93B1
+#ifndef GL_COMPRESSED_RGBA_ASTC_5x4_KHR
+#define GL_COMPRESSED_RGBA_ASTC_5x4_KHR 0x93B1
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_5x5_KHR
-#define COMPRESSED_RGBA_ASTC_5x5_KHR 0x93B2
+#ifndef GL_COMPRESSED_RGBA_ASTC_5x5_KHR
+#define GL_COMPRESSED_RGBA_ASTC_5x5_KHR 0x93B2
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_6x5_KHR
-#define COMPRESSED_RGBA_ASTC_6x5_KHR 0x93B3
+#ifndef GL_COMPRESSED_RGBA_ASTC_6x5_KHR
+#define GL_COMPRESSED_RGBA_ASTC_6x5_KHR 0x93B3
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_6x6_KHR
-#define COMPRESSED_RGBA_ASTC_6x6_KHR 0x93B4
+#ifndef GL_COMPRESSED_RGBA_ASTC_6x6_KHR
+#define GL_COMPRESSED_RGBA_ASTC_6x6_KHR 0x93B4
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_8x5_KHR
-#define COMPRESSED_RGBA_ASTC_8x5_KHR 0x93B5
+#ifndef GL_COMPRESSED_RGBA_ASTC_8x5_KHR
+#define GL_COMPRESSED_RGBA_ASTC_8x5_KHR 0x93B5
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_8x6_KHR
-#define COMPRESSED_RGBA_ASTC_8x6_KHR 0x93B6
+#ifndef GL_COMPRESSED_RGBA_ASTC_8x6_KHR
+#define GL_COMPRESSED_RGBA_ASTC_8x6_KHR 0x93B6
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_8x8_KHR
-#define COMPRESSED_RGBA_ASTC_8x8_KHR 0x93B7
+#ifndef GL_COMPRESSED_RGBA_ASTC_8x8_KHR
+#define GL_COMPRESSED_RGBA_ASTC_8x8_KHR 0x93B7
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_10x5_KHR
-#define COMPRESSED_RGBA_ASTC_10x5_KHR 0x93B8
+#ifndef GL_COMPRESSED_RGBA_ASTC_10x5_KHR
+#define GL_COMPRESSED_RGBA_ASTC_10x5_KHR 0x93B8
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_10x6_KHR
-#define COMPRESSED_RGBA_ASTC_10x6_KHR 0x93B9
+#ifndef GL_COMPRESSED_RGBA_ASTC_10x6_KHR
+#define GL_COMPRESSED_RGBA_ASTC_10x6_KHR 0x93B9
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_10x8_KHR
-#define COMPRESSED_RGBA_ASTC_10x8_KHR 0x93BA
+#ifndef GL_COMPRESSED_RGBA_ASTC_10x8_KHR
+#define GL_COMPRESSED_RGBA_ASTC_10x8_KHR 0x93BA
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_10x10_KHR
-#define COMPRESSED_RGBA_ASTC_10x10_KHR 0x93BB
+#ifndef GL_COMPRESSED_RGBA_ASTC_10x10_KHR
+#define GL_COMPRESSED_RGBA_ASTC_10x10_KHR 0x93BB
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_12x10_KHR
-#define COMPRESSED_RGBA_ASTC_12x10_KHR 0x93BC
+#ifndef GL_COMPRESSED_RGBA_ASTC_12x10_KHR
+#define GL_COMPRESSED_RGBA_ASTC_12x10_KHR 0x93BC
 #endif
 
-#ifndef COMPRESSED_RGBA_ASTC_12x12_KHR
-#define COMPRESSED_RGBA_ASTC_12x12_KHR 0x93BD
+#ifndef GL_COMPRESSED_RGBA_ASTC_12x12_KHR
+#define GL_COMPRESSED_RGBA_ASTC_12x12_KHR 0x93BD
 #endif
 
 #endif
diff --git a/IO/src/ImageLoaderKTX.cpp b/IO/src/ImageLoaderKTX.cpp
index 3d57a37..aab12fd 100644
--- a/IO/src/ImageLoaderKTX.cpp
+++ b/IO/src/ImageLoaderKTX.cpp
@@ -244,59 +244,72 @@ bool ImageLoaderKTX::ReadData() {
         m_Format = FasTC::eCompressionFormat_BPTC;
         break;
 
-      case COMPRESSED_RGBA_ASTC_4x4_KHR:
+      case GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG:
+      case GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG:
+        m_Format = FasTC::eCompressionFormat_PVRTC4;
+        break;
+
+      case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
+        m_Format = FasTC::eCompressionFormat_DXT1;
+        break;
+
+      case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
+        m_Format = FasTC::eCompressionFormat_DXT5;
+        break;
+
+      case GL_COMPRESSED_RGBA_ASTC_4x4_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC4x4;
         break;
 
-      case COMPRESSED_RGBA_ASTC_5x4_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_5x4_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC5x4;
         break;
 
-      case COMPRESSED_RGBA_ASTC_5x5_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_5x5_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC5x5;
         break;
 
-      case COMPRESSED_RGBA_ASTC_6x5_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_6x5_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC6x5;
         break;
 
-      case COMPRESSED_RGBA_ASTC_6x6_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_6x6_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC6x6;
         break;
 
-      case COMPRESSED_RGBA_ASTC_8x5_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_8x5_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC8x5;
         break;
 
-      case COMPRESSED_RGBA_ASTC_8x6_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_8x6_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC8x6;
         break;
 
-      case COMPRESSED_RGBA_ASTC_8x8_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_8x8_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC8x8;
         break;
 
-      case COMPRESSED_RGBA_ASTC_10x5_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_10x5_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC10x5;
         break;
 
-      case COMPRESSED_RGBA_ASTC_10x6_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_10x6_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC10x6;
         break;
 
-      case COMPRESSED_RGBA_ASTC_10x8_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_10x8_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC10x8;
         break;
 
-      case COMPRESSED_RGBA_ASTC_10x10_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_10x10_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC10x10;
         break;
 
-      case COMPRESSED_RGBA_ASTC_12x10_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_12x10_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC12x10;
         break;
 
-      case COMPRESSED_RGBA_ASTC_12x12_KHR:
+      case GL_COMPRESSED_RGBA_ASTC_12x12_KHR:
         m_Format = FasTC::eCompressionFormat_ASTC12x12;
         break;
 
diff --git a/IO/src/ImageWriterKTX.cpp b/IO/src/ImageWriterKTX.cpp
index b572359..580bb8b 100644
--- a/IO/src/ImageWriterKTX.cpp
+++ b/IO/src/ImageWriterKTX.cpp
@@ -97,7 +97,17 @@ bool ImageWriterKTX::WriteImage() {
       break;
 
     case FasTC::eCompressionFormat_PVRTC4:
-      wtr.Write(COMPRESSED_RGBA_PVRTC_4BPPV1_IMG);  // glInternalFormat
+      wtr.Write(GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG);  // glInternalFormat
+      wtr.Write(GL_RGBA);  // glBaseFormat
+      break;
+
+    case FasTC::eCompressionFormat_DXT1:
+      wtr.Write(GL_COMPRESSED_RGB_S3TC_DXT1_EXT);  // glInternalFormat
+      wtr.Write(GL_RGB);  // glBaseFormat
+      break;
+
+    case FasTC::eCompressionFormat_DXT5:
+      wtr.Write(GL_COMPRESSED_RGBA_S3TC_DXT5_EXT);  // glInternalFormat
       wtr.Write(GL_RGBA);  // glBaseFormat
       break;
 
@@ -127,11 +137,15 @@ bool ImageWriterKTX::WriteImage() {
   wtr.Write(orientationValue, oValLen + 1); // value
   wtr.Write(orientationKey, tkvSz - kvSz - 4); // padding
 
-  if(ci && ci->GetFormat() == FasTC::eCompressionFormat_BPTC) {
+  if(ci &&
+     (ci->GetFormat() == FasTC::eCompressionFormat_BPTC ||
+      ci->GetFormat() == FasTC::eCompressionFormat_DXT5)) {
     static const uint32 kImageSize = m_Width * m_Height;
     wtr.Write(kImageSize); // imageSize
     wtr.Write(ci->GetCompressedData(), kImageSize); // imagedata...
-  } else if(ci && ci->GetFormat() == FasTC::eCompressionFormat_PVRTC4) {
+  } else if(ci &&
+            (ci->GetFormat() == FasTC::eCompressionFormat_PVRTC4 ||
+             ci->GetFormat() == FasTC::eCompressionFormat_DXT1)) {
     static const uint32 kImageSize = m_Width * m_Height >> 1;
     wtr.Write(kImageSize); // imageSize
     wtr.Write(ci->GetCompressedData(), kImageSize); // imagedata...