diff --git a/src/shaders/editor_functions.glsl b/src/shaders/editor_functions.glsl
index 563ad5d2..48fe84f1 100644
--- a/src/shaders/editor_functions.glsl
+++ b/src/shaders/editor_functions.glsl
@@ -12,7 +12,8 @@ R"(
 
 
 //INSERT: EDITOR_COMPATIBILITY_DEFINES
-// Compatibility overrides
+// COMPATIBILITY_DEFINES
+// This is added automatically when in compatibility mode. It is not required for Mobile or Forward+
 #define fma(a, b, c) (a) * (b) + (c)
 #define dFdxCoarse(a) dFdx(a)
 #define dFdyCoarse(a) dFdy(a)
diff --git a/src/terrain_3d_material.cpp b/src/terrain_3d_material.cpp
index a86f6635..2963f4d8 100644
--- a/src/terrain_3d_material.cpp
+++ b/src/terrain_3d_material.cpp
@@ -155,7 +155,7 @@ String Terrain3DMaterial::_inject_editor_code(const String &p_shader) const {
 	// Insert at the very begining
 	idx = 0;
 	insert_names.clear();
-	if (_compatibility) {
+	if (_compatibility && !shader.contains("COMPATIBILITY_DEFINES")) {
 		insert_names.push_back("EDITOR_COMPATIBILITY_DEFINES");
 	}
 	for (int i = 0; i < insert_names.size(); i++) {
@@ -253,6 +253,10 @@ void Terrain3DMaterial::_update_shader() {
 		if (_shader_override->get_code().is_empty()) {
 			_shader_override->set_code(_generate_shader_code());
 		}
+		// 
+		if (_compatibility && !_shader_override->get_code().contains("COMPATIBILITY_DEFINES")) {
+			_shader_override->set_code(_shader_override->get_code().insert(0, _shader_code["EDITOR_COMPATIBILITY_DEFINES"]));
+		}
 		code = _shader_override->get_code();
 		if (!_shader_override->is_connected("changed", callable_mp(this, &Terrain3DMaterial::_update_shader))) {
 			LOG(DEBUG, "Connecting changed signal to _update_shader()");