diff --git a/drivers/gles3/shaders/canvas.glsl b/drivers/gles3/shaders/canvas.glsl
index ea0a0b660df..ae3892fb61a 100644
--- a/drivers/gles3/shaders/canvas.glsl
+++ b/drivers/gles3/shaders/canvas.glsl
@@ -589,7 +589,7 @@ void main() {
 		if (bool(read_draw_data_flags & FLAGS_FLIP_V)) {
 			normal.y = -normal.y;
 		}
-		normal.z = sqrt(1.0 - dot(normal.xy, normal.xy));
+		normal.z = sqrt(max(0.0, 1.0 - dot(normal.xy, normal.xy)));
 		normal_used = true;
 	} else {
 		normal = vec3(0.0, 0.0, 1.0);
diff --git a/servers/rendering/renderer_rd/shaders/canvas.glsl b/servers/rendering/renderer_rd/shaders/canvas.glsl
index 1fb8b28b154..c96524b5c93 100644
--- a/servers/rendering/renderer_rd/shaders/canvas.glsl
+++ b/servers/rendering/renderer_rd/shaders/canvas.glsl
@@ -508,7 +508,7 @@ void main() {
 		if (bool(draw_data.flags & FLAGS_FLIP_V)) {
 			normal.y = -normal.y;
 		}
-		normal.z = sqrt(1.0 - dot(normal.xy, normal.xy));
+		normal.z = sqrt(max(0.0, 1.0 - dot(normal.xy, normal.xy)));
 		normal_used = true;
 	} else {
 		normal = vec3(0.0, 0.0, 1.0);