diff --git a/addons/material_maker/engine/gen_base.gd b/addons/material_maker/engine/gen_base.gd
index fbcc96e..5ed2767 100644
--- a/addons/material_maker/engine/gen_base.gd
+++ b/addons/material_maker/engine/gen_base.gd
@@ -8,6 +8,8 @@ Base class for texture generators, that defines their API
 
 signal parameter_changed(n, v)
 
+const DEFAULT_GENERATED_SHADER : Dictionary = { defs="", code="", textures={}, type="f", f="0.0" }
+
 class InputPort:
 	var generator : MMGenBase = null
 	var input_index : int = 0
@@ -232,7 +234,7 @@ func render(output_index : int, size : int, preview : bool = false) -> Object:
 	while source is GDScriptFunctionState:
 		source = yield(source, "completed")
 	if source.empty():
-		source = { defs="", code="", textures={}, rgba="vec4(0.0)" }
+		source = DEFAULT_GENERATED_SHADER
 	var shader : String
 	if preview:
 		var output_type = "rgba"
diff --git a/addons/material_maker/engine/gen_buffer.gd b/addons/material_maker/engine/gen_buffer.gd
index 04750f6..42f69db 100644
--- a/addons/material_maker/engine/gen_buffer.gd
+++ b/addons/material_maker/engine/gen_buffer.gd
@@ -48,7 +48,7 @@ func update_shader() -> void:
 		while source is GDScriptFunctionState:
 			source = yield(source, "completed")
 	if source.empty():
-		source = { defs="", code="", textures={}, rgba="vec4(0.0)" }
+		source = DEFAULT_GENERATED_SHADER
 	material.shader.code = mm_renderer.generate_shader(source)
 	if source.has("textures"):
 		for k in source.textures.keys():
diff --git a/addons/material_maker/engine/gen_graph.gd b/addons/material_maker/engine/gen_graph.gd
index e34675d..69f8497 100644
--- a/addons/material_maker/engine/gen_graph.gd
+++ b/addons/material_maker/engine/gen_graph.gd
@@ -62,9 +62,10 @@ func get_parameter_defs() -> Array:
 		return get_node("gen_parameters").get_parameter_defs()
 	return []
 
-func set_parameter(p, v) -> void:
+func set_parameter(n : String, v) -> void:
+	.set_parameter(n, v)
 	if has_node("gen_parameters"):
-		get_node("gen_parameters").set_parameter(p, v)
+		get_node("gen_parameters").set_parameter(n, v)
 
 func get_input_defs() -> Array:
 	if has_node("gen_inputs"):
diff --git a/addons/material_maker/engine/gen_ios.gd b/addons/material_maker/engine/gen_ios.gd
index 3e2437f..37e7c16 100644
--- a/addons/material_maker/engine/gen_ios.gd
+++ b/addons/material_maker/engine/gen_ios.gd
@@ -95,7 +95,7 @@ func _get_shader_code(uv : String, output_index : int, context : MMGenContext) -
 		while rv is GDScriptFunctionState:
 			rv = yield(rv, "completed")
 		return rv
-	return { defs="", code="", textures={} }
+	return DEFAULT_GENERATED_SHADER
 
 func _serialize(data: Dictionary) -> Dictionary:
 	data.type = "ios"
diff --git a/addons/material_maker/engine/gen_material.gd b/addons/material_maker/engine/gen_material.gd
index 7d57fd0..4864f93 100644
--- a/addons/material_maker/engine/gen_material.gd
+++ b/addons/material_maker/engine/gen_material.gd
@@ -98,7 +98,7 @@ func render_textures() -> void:
 			while source is GDScriptFunctionState:
 				source = yield(source, "completed")
 			if source.empty():
-				source = { defs="", code="", textures={}, rgba="vec4(0.0)" }
+				source = DEFAULT_GENERATED_SHADER
 			shader_materials[t.texture].shader.code = mm_renderer.generate_shader(source)
 			if source.has("textures"):
 				for k in source.textures.keys():
diff --git a/material_maker/preview/preview_2d.gd b/material_maker/preview/preview_2d.gd
index ab0f98d..54f70df 100644
--- a/material_maker/preview/preview_2d.gd
+++ b/material_maker/preview/preview_2d.gd
@@ -8,7 +8,7 @@ var output : int = 0
 func set_generator(g : MMGenBase, o : int = 0) -> void:
 	if is_instance_valid(generator):
 		generator.disconnect("parameter_changed", self, "on_parameter_changed")
-	var source = { defs="", code="", textures={}, type="f", f="1.0" }
+	var source = MMGenBase.DEFAULT_GENERATED_SHADER
 	if is_instance_valid(g):
 		generator = g
 		output = o
@@ -23,7 +23,7 @@ func set_generator(g : MMGenBase, o : int = 0) -> void:
 			while source is GDScriptFunctionState:
 				source = yield(source, "completed")
 			if source.empty():
-				source = { defs="", code="", textures={}, type="f", f="1.0" }
+				source = MMGenBase.DEFAULT_GENERATED_SHADER
 	else:
 		g = null
 		for c in get_children():
diff --git a/material_maker/widgets/histogram/histogram.gd b/material_maker/widgets/histogram/histogram.gd
index 4b6b867..b57a887 100644
--- a/material_maker/widgets/histogram/histogram.gd
+++ b/material_maker/widgets/histogram/histogram.gd
@@ -15,7 +15,7 @@ func get_histogram_texture() -> ImageTexture:
 func set_generator(g : MMGenBase, o : int = 0) -> void:
 	if is_instance_valid(generator):
 		generator.disconnect("parameter_changed", self, "on_parameter_changed")
-	var source = { defs="", code="", textures={}, type="f", f="1.0" }
+	var source = MMGenBase.DEFAULT_GENERATED_SHADER
 	if is_instance_valid(g):
 		generator = g
 		output = o
@@ -28,7 +28,7 @@ func set_generator(g : MMGenBase, o : int = 0) -> void:
 			while source is GDScriptFunctionState:
 				source = yield(source, "completed")
 			if source.empty():
-				source = { defs="", code="", textures={}, type="f", f="1.0" }
+				source = MMGenBase.DEFAULT_GENERATED_SHADER
 	# Update shader
 	$ViewportImage/ColorRect.material.shader.code = MMGenBase.generate_preview_shader(source, source.type, "uniform vec2 size;void fragment() {COLOR = preview_2d(UV);}")
 	# Get parameter values from the shader code