diff --git a/src/edwards.rs b/src/edwards.rs
index 53f1499..e03230b 100644
--- a/src/edwards.rs
+++ b/src/edwards.rs
@@ -190,11 +190,10 @@ impl CompressedEdwardsY {
 
         if is_valid_y_coord.unwrap_u8() != 1u8 { return None; }
 
-        // Flip the sign of X if it's not correct
+         // FieldElement::sqrt_ratio_i always returns the nonnegative square root,
+         // so we negate according to the supplied sign bit.
         let compressed_sign_bit = Choice::from(self.as_bytes()[31] >> 7);
-        let    current_sign_bit = X.is_negative();
-
-        X.conditional_negate(current_sign_bit ^ compressed_sign_bit);
+        X.conditional_negate(compressed_sign_bit);
 
         Some(EdwardsPoint{ X: X, Y: Y, Z: Z, T: &X * &Y })
     }