diff --git a/components/style/gecko/media_queries.rs b/components/style/gecko/media_queries.rs
index 53074d9058a..d6c5a9286bd 100644
--- a/components/style/gecko/media_queries.rs
+++ b/components/style/gecko/media_queries.rs
@@ -409,11 +409,12 @@ impl Expression {
             // If there's no colon, this is a media query of the form
             // '(<feature>)', that is, there's no value specified.
             //
-            // FIXME(emilio): We need to check for range operators too here when
-            // we support them, see:
-            //
-            // https://drafts.csswg.org/mediaqueries/#mq-ranges
+            // Gecko doesn't allow ranged expressions without a value, so just
+            // reject them here too.
             if input.try(|i| i.expect_colon()).is_err() {
+                if range != nsMediaExpression_Range::eEqual {
+                    return Err(())
+                }
                 return Ok(Expression::new(feature, None, range));
             }
 
diff --git a/components/style/media_queries.rs b/components/style/media_queries.rs
index e9336515e9c..8a50282682b 100644
--- a/components/style/media_queries.rs
+++ b/components/style/media_queries.rs
@@ -56,10 +56,10 @@ impl ToCss for Qualifier {
     fn to_css<W>(&self, dest: &mut W) -> fmt::Result
         where W: fmt::Write
     {
-        match *self {
-            Qualifier::Not => write!(dest, "not"),
-            Qualifier::Only => write!(dest, "only"),
-        }
+        dest.write_str(match *self {
+            Qualifier::Not => "not",
+            Qualifier::Only => "only",
+        })
     }
 }
 
@@ -152,15 +152,26 @@ pub enum MediaQueryType {
 }
 
 impl MediaQueryType {
-    fn parse(ident: &str) -> Self {
+    fn parse(ident: &str) -> Result<Self, ()> {
         if ident.eq_ignore_ascii_case("all") {
-            return MediaQueryType::All;
+            return Ok(MediaQueryType::All);
         }
 
-        match MediaType::parse(ident) {
+        // From https://drafts.csswg.org/mediaqueries/#mq-syntax:
+        //
+        //   The <media-type> production does not include the keywords only,
+        //   not, and, and or.
+        if ident.eq_ignore_ascii_case("not") ||
+           ident.eq_ignore_ascii_case("or") ||
+           ident.eq_ignore_ascii_case("and") ||
+           ident.eq_ignore_ascii_case("only") {
+            return Err(())
+        }
+
+        Ok(match MediaType::parse(ident) {
             Some(media_type) => MediaQueryType::Known(media_type),
             None => MediaQueryType::Unknown(Atom::from(ident)),
-        }
+        })
     }
 
     fn matches(&self, other: MediaType) -> bool {
@@ -207,7 +218,7 @@ impl MediaQuery {
         };
 
         let media_type = match input.try(|input| input.expect_ident()) {
-            Ok(ident) => MediaQueryType::parse(&*ident),
+            Ok(ident) => try!(MediaQueryType::parse(&*ident)),
             Err(()) => {
                 // Media type is only optional if qualifier is not specified.
                 if qualifier.is_some() {