diff --git a/drivers/gles2/shaders/canvas.glsl b/drivers/gles2/shaders/canvas.glsl
index 444839ff9ba0..b6371980cdae 100644
--- a/drivers/gles2/shaders/canvas.glsl
+++ b/drivers/gles2/shaders/canvas.glsl
@@ -455,7 +455,7 @@ void main() {
 
 	if (use_default_normal) {
 		normal.xy = texture2D(normal_texture, uv).xy * 2.0 - 1.0;
-		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/drivers/gles3/shaders/canvas.glsl b/drivers/gles3/shaders/canvas.glsl
index 9a1122c92067..620968cd143b 100644
--- a/drivers/gles3/shaders/canvas.glsl
+++ b/drivers/gles3/shaders/canvas.glsl
@@ -549,7 +549,7 @@ void main() {
 
 	if (use_default_normal) {
 		normal.xy = textureLod(normal_texture, uv, 0.0).xy * 2.0 - 1.0;
-		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);