diff --git a/implementations/rust/oo/src/text/writer.rs b/implementations/rust/oo/src/text/writer.rs
index 2e549fc..d7791dd 100644
--- a/implementations/rust/oo/src/text/writer.rs
+++ b/implementations/rust/oo/src/text/writer.rs
@@ -208,22 +208,22 @@ impl<W: io::Write> Writer for TextWriter<W> {
     }
 
     fn write_f32(&mut self, v: f32) -> io::Result<()> {
-        if f32::is_normal(v) || f32::is_subnormal(v) {
+        if v.is_nan() || v.is_infinite() {
+            write!(self.w, "#xf\"{}\"",
+                   HexFormatter::Packed.encode(&u32::to_be_bytes(f32::to_bits(v))))
+        } else {
             dtoa::write(&mut self.w, v)?;
             write!(self.w, "f")
-        } else {
-            let bs = v.to_be_bytes();
-            write!(self.w, "#xf\"{}\"", HexFormatter::Packed.encode(&bs))
         }
     }
 
     fn write_f64(&mut self, v: f64) -> io::Result<()> {
-        if f64::is_normal(v) || f64::is_subnormal(v) {
+        if v.is_nan() || v.is_infinite() {
+            write!(self.w, "#xd\"{}\"",
+                   HexFormatter::Packed.encode(&u64::to_be_bytes(f64::to_bits(v))))
+        } else {
             dtoa::write(&mut self.w, v)?;
             Ok(())
-        } else {
-            let bs = v.to_be_bytes();
-            write!(self.w, "#xd\"{}\"", HexFormatter::Packed.encode(&bs))
         }
     }