diff --git a/Ryujinx.Graphics/Gal/Shader/GlslDecl.cs b/Ryujinx.Graphics/Gal/Shader/GlslDecl.cs
index b144cef306..3489a040d5 100644
--- a/Ryujinx.Graphics/Gal/Shader/GlslDecl.cs
+++ b/Ryujinx.Graphics/Gal/Shader/GlslDecl.cs
@@ -6,6 +6,7 @@ namespace Ryujinx.Graphics.Gal.Shader
     class GlslDecl
     {
         public const int LayerAttr       = 0x064;
+        public const int ViewportIdxAttr = 0x068;
         public const int PointSizeAttr   = 0x06c;
         public const int PointCoordAttrX = 0x2e0;
         public const int PointCoordAttrY = 0x2e4;
diff --git a/Ryujinx.Graphics/Gal/Shader/GlslDecompiler.cs b/Ryujinx.Graphics/Gal/Shader/GlslDecompiler.cs
index e6fb7ea147..7be7d0a744 100644
--- a/Ryujinx.Graphics/Gal/Shader/GlslDecompiler.cs
+++ b/Ryujinx.Graphics/Gal/Shader/GlslDecompiler.cs
@@ -190,7 +190,13 @@ namespace Ryujinx.Graphics.Gal.Shader
 
         private void PrintDeclHeader()
         {
-            if (Decl.ShaderType == GalShaderType.Geometry)
+            if(Decl.ShaderType == GalShaderType.Vertex)
+            {
+                SB.AppendLine("#extension GL_AMD_vertex_shader_viewport_index : require");
+
+                SB.AppendLine();
+            }
+            else if (Decl.ShaderType == GalShaderType.Geometry)
             {
                 int MaxVertices = Header.MaxOutputVertexCount;
 
@@ -872,10 +878,18 @@ namespace Ryujinx.Graphics.Gal.Shader
 
                     return Name + Swizzle;
                 }
+                else if (Abuf.Offs == GlslDecl.ViewportIdxAttr)
+                {
+                    return "gl_ViewportIndex";
+                }
                 else if (Abuf.Offs == GlslDecl.PointSizeAttr)
                 {
                     return "gl_PointSize";
                 }
+                else
+                {
+                    throw new NotImplementedException($"Attribute with offset 0x{Abuf.Offs:x2} is not implemented.");
+                }
             }
 
             if (DeclInfo.Index >= 32)
@@ -1346,9 +1360,10 @@ namespace Ryujinx.Graphics.Gal.Shader
             switch (Node)
             {
                 case ShaderIrOperAbuf Abuf:
-                    return Abuf.Offs == GlslDecl.LayerAttr      ||
-                           Abuf.Offs == GlslDecl.InstanceIdAttr ||
-                           Abuf.Offs == GlslDecl.VertexIdAttr   ||
+                    return Abuf.Offs == GlslDecl.LayerAttr       ||
+                           Abuf.Offs == GlslDecl.ViewportIdxAttr ||
+                           Abuf.Offs == GlslDecl.InstanceIdAttr  ||
+                           Abuf.Offs == GlslDecl.VertexIdAttr    ||
                            Abuf.Offs == GlslDecl.FaceAttr
                         ? OperType.I32
                         : OperType.F32;