diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index 5aa839874b4..58c14b71376 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -909,15 +909,26 @@ impl ToCss for Percentage {
     }
 }
 
+impl Percentage {
+    fn parse_internal(input: &mut Parser, context: AllowedNumericType) -> Result<Self, ()> {
+        match try!(input.next()) {
+            Token::Percentage(ref value) if context.is_ok(value.unit_value) => {
+                Ok(Percentage(value.unit_value))
+            }
+            _ => Err(())
+        }
+    }
+
+    /// Parses a percentage token, but rejects it if it's negative.
+    pub fn parse_non_negative(input: &mut Parser) -> Result<Self, ()> {
+        Self::parse_internal(input, AllowedNumericType::NonNegative)
+    }
+}
+
 impl Parse for Percentage {
     #[inline]
     fn parse(_context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
-        let context = AllowedNumericType::All;
-        match try!(input.next()) {
-            Token::Percentage(ref value) if context.is_ok(value.unit_value) =>
-                Ok(Percentage(value.unit_value)),
-            _ => Err(())
-        }
+        Self::parse_internal(input, AllowedNumericType::All)
     }
 }
 
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 1a7fda7a673..1cea83d5329 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -538,8 +538,8 @@ impl Parse for Number {
 impl Number {
     fn parse_with_minimum(input: &mut Parser, min: CSSFloat) -> Result<Number, ()> {
         match parse_number(input) {
-            Ok(value) if value < min => Err(()),
-            value => value.map(Number),
+            Ok(value) if value >= min => Ok(Number(value)),
+            _ => Err(()),
         }
     }
 
@@ -585,13 +585,12 @@ pub enum NumberOrPercentage {
 no_viewport_percentage!(NumberOrPercentage);
 
 impl Parse for NumberOrPercentage {
-    fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
-        if let Ok(per) = input.try(|input| Percentage::parse(context, input)) {
+    fn parse(_context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
+        if let Ok(per) = input.try(Percentage::parse_non_negative) {
             return Ok(NumberOrPercentage::Percentage(per));
         }
 
-        let num = try!(Number::parse_non_negative(input));
-        Ok(NumberOrPercentage::Number(num))
+        Number::parse_non_negative(input).map(NumberOrPercentage::Number)
     }
 }