diff --git a/crates/toml/tests/testsuite/float.rs b/crates/toml/tests/testsuite/float.rs
index d0081347..d0bf957b 100644
--- a/crates/toml/tests/testsuite/float.rs
+++ b/crates/toml/tests/testsuite/float.rs
@@ -47,7 +47,7 @@ macro_rules! float_inf_tests {
         assert!(inf.sf5.is_nan());
         assert!(inf.sf5.is_sign_positive());
         assert!(inf.sf6.is_nan());
-        assert!(inf.sf6.is_sign_negative());
+        assert!(inf.sf6.is_sign_negative()); // NOTE: but serializes to just `nan`
 
         assert_eq!(inf.sf7, 0.0);
         assert!(inf.sf7.is_sign_positive());
@@ -63,7 +63,7 @@ sf2 = inf
 sf3 = -inf
 sf4 = nan
 sf5 = nan
-sf6 = -nan
+sf6 = nan
 sf7 = 0.0
 sf8 = -0.0
 "
diff --git a/crates/toml_edit/src/encode.rs b/crates/toml_edit/src/encode.rs
index db10e29e..e4d8cb1f 100644
--- a/crates/toml_edit/src/encode.rs
+++ b/crates/toml_edit/src/encode.rs
@@ -537,8 +537,7 @@ impl ValueRepr for f64 {
 
 fn to_f64_repr(f: f64) -> Repr {
     let repr = match (f.is_sign_negative(), f.is_nan(), f == 0.0) {
-        (true, true, _) => "-nan".to_owned(),
-        (false, true, _) => "nan".to_owned(),
+        (_, true, _) => "nan".to_owned(),
         (true, false, true) => "-0.0".to_owned(),
         (false, false, true) => "0.0".to_owned(),
         (_, false, false) => {