diff --git a/components/style/properties/shorthand/box.mako.rs b/components/style/properties/shorthand/box.mako.rs
index 209d33eb7b4..d838039c68c 100644
--- a/components/style/properties/shorthand/box.mako.rs
+++ b/components/style/properties/shorthand/box.mako.rs
@@ -176,7 +176,7 @@ macro_rules! try_parse_one {
 
             for i in 0..len {
                 if i != 0 {
-                    write!(dest, ", ")?;
+                    dest.write_str(", ")?;
                 }
                 self.transition_property.0[i].to_css(dest)?;
                 % for name in "duration timing_function delay".split():
@@ -289,7 +289,7 @@ macro_rules! try_parse_one {
 
             for i in 0..len {
                 if i != 0 {
-                    write!(dest, ", ")?;
+                    dest.write_str(", ")?;
                 }
 
                 % for name in props[1:]:
diff --git a/components/style/values/generics/mod.rs b/components/style/values/generics/mod.rs
index 16f90ec11a2..239b104d49d 100644
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@@ -226,7 +226,10 @@ impl ToCss for FontSettingTagInt {
         match self.0 {
             1 => Ok(()),
             0 => dest.write_str(" off"),
-            x => write!(dest, " {}", x)
+            x => {
+                dest.write_char(' ')?;
+                x.to_css(dest)
+            }
         }
     }
 }
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index c816e542020..3789a544669 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -424,7 +424,11 @@ impl ToCss for NoCalcLength {
             NoCalcLength::FontRelative(length) => length.to_css(dest),
             NoCalcLength::ViewportPercentage(length) => length.to_css(dest),
             /* This should only be reached from style dumping code */
-            NoCalcLength::ServoCharacterWidth(CharacterWidth(i)) => write!(dest, "CharWidth({})", i),
+            NoCalcLength::ServoCharacterWidth(CharacterWidth(i)) => {
+                dest.write_str("CharWidth(")?;
+                i.to_css(dest)?;
+                dest.write_char(')')
+            }
             #[cfg(feature = "gecko")]
             NoCalcLength::Physical(length) => length.to_css(dest),
         }