diff --git a/internal/shaderir/glsl.go b/internal/shaderir/glsl.go
index b00373182..dfdc51c24 100644
--- a/internal/shaderir/glsl.go
+++ b/internal/shaderir/glsl.go
@@ -193,6 +193,8 @@ func (p *Program) glslBlock(b *Block, level int, localVarIndex int) []string {
 			switch e.Variable.Type {
 			case Uniform:
 				return fmt.Sprintf("U%d", e.Variable.Index)
+			case StructMember:
+				return fmt.Sprintf("M%d", e.Variable.Index)
 			case Local:
 				idx := e.Variable.Index
 				switch b {
diff --git a/internal/shaderir/program.go b/internal/shaderir/program.go
index 6ff7b161a..ea04fd396 100644
--- a/internal/shaderir/program.go
+++ b/internal/shaderir/program.go
@@ -119,6 +119,7 @@ type VariableType int
 
 const (
 	Uniform VariableType = iota
+	StructMember
 	Local
 )