diff --git a/internal/shaderir/glsl.go b/internal/shaderir/glsl.go
index 399150c40..9ef4f6f3b 100644
--- a/internal/shaderir/glsl.go
+++ b/internal/shaderir/glsl.go
@@ -58,6 +58,13 @@ func (p *Program) Glsl() string {
 		lines = append(lines, "}")
 	}
 
+	// Fragment func
+	if len(p.FragmentFunc.Block.Stmts) > 0 {
+		lines = append(lines, "void main(void) {")
+		lines = append(lines, p.glslBlock(&p.FragmentFunc.Block, 0, 0)...)
+		lines = append(lines, "}")
+	}
+
 	var stLines []string
 	for i, t := range p.structTypes {
 		stLines = append(stLines, fmt.Sprintf("struct S%d {", i))
@@ -151,7 +158,8 @@ func (p *Program) glslBlock(b *Block, level int, localVarIndex int) []string {
 				return fmt.Sprintf("U%d", e.Variable.Index)
 			case Local:
 				idx := e.Variable.Index
-				if b == &p.VertexFunc.Block {
+				switch b {
+				case &p.VertexFunc.Block:
 					na := len(p.Attributes)
 					nv := len(p.Varyings)
 					switch {
@@ -162,9 +170,19 @@ func (p *Program) glslBlock(b *Block, level int, localVarIndex int) []string {
 					case idx == na+nv:
 						return "gl_Position"
 					default:
-						return fmt.Sprintf("l%d", idx-(na+nv))
+						return fmt.Sprintf("l%d", idx-(na+nv+1))
 					}
-				} else {
+				case &p.FragmentFunc.Block:
+					nv := len(p.Varyings)
+					switch {
+					case idx < nv:
+						return fmt.Sprintf("V%d", idx)
+					case idx == nv:
+						return "gl_FragCoord"
+					default:
+						return fmt.Sprintf("l%d", idx-(nv+1))
+					}
+				default:
 					return fmt.Sprintf("l%d", idx)
 				}
 			default:
diff --git a/internal/shaderir/ir_test.go b/internal/shaderir/ir_test.go
index 422707d05..226911871 100644
--- a/internal/shaderir/ir_test.go
+++ b/internal/shaderir/ir_test.go
@@ -566,6 +566,80 @@ void main(void) {
 	gl_Position = A0;
 	V0 = A1;
 	V1 = A2;
+}`,
+		},
+		{
+			Name: "FragmentFunc",
+			Program: Program{
+				Uniforms: []Type{
+					{Main: Float},
+				},
+				Attributes: []Type{
+					{Main: Vec4},
+					{Main: Float},
+					{Main: Vec2},
+				},
+				Varyings: []Type{
+					{Main: Float},
+					{Main: Vec2},
+				},
+				VertexFunc: VertexFunc{
+					Block: block(
+						nil,
+						assignStmt(
+							varNameExpr(Local, 5),
+							varNameExpr(Local, 0),
+						),
+						assignStmt(
+							varNameExpr(Local, 3),
+							varNameExpr(Local, 1),
+						),
+						assignStmt(
+							varNameExpr(Local, 4),
+							varNameExpr(Local, 2),
+						),
+					),
+				},
+				FragmentFunc: FragmentFunc{
+					Block: block(
+						[]Type{
+							{Main: Vec2},
+							{Main: Vec4},
+							{Main: Float},
+						},
+						assignStmt(
+							varNameExpr(Local, 5),
+							varNameExpr(Local, 0),
+						),
+						assignStmt(
+							varNameExpr(Local, 3),
+							varNameExpr(Local, 1),
+						),
+						assignStmt(
+							varNameExpr(Local, 4),
+							varNameExpr(Local, 2),
+						),
+					),
+				},
+			},
+			Glsl: `uniform float U0;
+attribute vec4 A0;
+attribute float A1;
+attribute vec2 A2;
+varying float V0;
+varying vec2 V1;
+void main(void) {
+	gl_Position = A0;
+	V0 = A1;
+	V1 = A2;
+}
+void main(void) {
+	vec2 l0;
+	vec4 l1;
+	float l2;
+	l2 = V0;
+	l0 = V1;
+	l1 = gl_FragCoord;
 }`,
 		},
 	}