diff --git a/src/curve.rs b/src/curve.rs
index 529f396..200dd19 100644
--- a/src/curve.rs
+++ b/src/curve.rs
@@ -159,7 +159,7 @@ impl CompressedEdwardsY {
             X *= &constants::SQRT_M1;
         }
 
-        if X.is_negative() != (self[31] >> 7) as i32 {
+        if X.is_negative_ed25519() != (self[31] >> 7) as i32 {
             X = X.neg();
         }
         T = &X * &Y;
@@ -391,7 +391,7 @@ impl ProjectivePoint {
         let mut s: [u8; 32];
 
         s      =  y.to_bytes();
-        s[31] ^= (x.is_negative() << 7) as u8;
+        s[31] ^= (x.is_negative_ed25519() << 7) as u8;
         CompressedEdwardsY(s)
     }
 }
diff --git a/src/field.rs b/src/field.rs
index f26108d..572b39f 100644
--- a/src/field.rs
+++ b/src/field.rs
@@ -510,13 +510,14 @@ impl FieldElement {
         (!equal_so_far & 1 & greater) as u8
     }
 
-    /// Determine if this `FieldElement` is negative.
+    /// Determine if this `FieldElement` is negative, in the
+    /// sense used in the ed25519 paper.
     ///
     /// # Return
     ///
     /// If negative, return `1i32`.  Otherwise, return `0i32`.
     // XXX should return u8
-    pub fn is_negative(&self) -> i32 { //FeIsNegative
+    pub fn is_negative_ed25519(&self) -> i32 { //FeIsNegative
         let bytes = self.to_bytes();
         (bytes[0] & 1) as i32
     }