diff --git a/components/style/parser.rs b/components/style/parser.rs
index 9874bf49f54..8bfefc414cb 100644
--- a/components/style/parser.rs
+++ b/components/style/parser.rs
@@ -20,6 +20,9 @@ bitflags! {
         /// to be in user units (px).
         /// https://www.w3.org/TR/SVG/coords.html#Units
         const PARSING_MODE_ALLOW_UNITLESS_LENGTH = 0x01,
+        /// In SVG, out-of-range values are not treated as an error in parsing.
+        /// https://www.w3.org/TR/SVG/implnote.html#RangeClamping
+        const PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES = 0x02,
     }
 }
 
@@ -28,6 +31,11 @@ impl ParsingMode {
     pub fn allows_unitless_lengths(&self) -> bool {
         self.intersects(PARSING_MODE_ALLOW_UNITLESS_LENGTH)
     }
+
+    /// Whether the parsing mode allows all numeric values.
+    pub fn allows_all_numeric_values(&self) -> bool {
+      self.intersects(PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES)
+    }
 }
 
 /// Asserts that all ParsingMode flags have a matching ParsingMode value in gecko.
@@ -39,12 +47,12 @@ pub fn assert_parsing_mode_match() {
     macro_rules! check_parsing_modes {
         ( $( $a:ident => $b:ident ),*, ) => {
             if cfg!(debug_assertions) {
-                let mut hints = ParsingMode::all();
+                let mut modes = ParsingMode::all();
                 $(
                     assert_eq!(structs::$a as usize, $b.bits() as usize, stringify!($b));
-                    hints.remove($b);
+                    modes.remove($b);
                 )*
-                assert_eq!(hints, ParsingMode::empty(), "all ParsingMode bits should have an assertion");
+                assert_eq!(modes, ParsingMode::empty(), "all ParsingMode bits should have an assertion");
             }
         }
     }
@@ -52,6 +60,7 @@ pub fn assert_parsing_mode_match() {
     check_parsing_modes! {
         ParsingMode_Default => PARSING_MODE_DEFAULT,
         ParsingMode_AllowUnitlessLength => PARSING_MODE_ALLOW_UNITLESS_LENGTH,
+        ParsingMode_AllowAllNumericValues => PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES,
     }
 }
 
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 8cd5ebdd793..31990fba71a 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -632,12 +632,20 @@ impl Number {
 
     #[allow(missing_docs)]
     pub fn parse_non_negative(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
-        parse_number_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+        if context.parsing_mode.allows_all_numeric_values() {
+            parse_number(context, input)
+        } else {
+            parse_number_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+        }
     }
 
     #[allow(missing_docs)]
     pub fn parse_at_least_one(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
-        parse_number_with_clamping_mode(context, input, AllowedNumericType::AtLeastOne)
+        if context.parsing_mode.allows_all_numeric_values() {
+            parse_number(context, input)
+        } else {
+            parse_number_with_clamping_mode(context, input, AllowedNumericType::AtLeastOne)
+        }
     }
 }
 
diff --git a/tests/unit/style/parsing/value.rs b/tests/unit/style/parsing/value.rs
index 2151529a293..3a1f69746e4 100644
--- a/tests/unit/style/parsing/value.rs
+++ b/tests/unit/style/parsing/value.rs
@@ -3,8 +3,13 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use app_units::Au;
+use cssparser::Parser;
+use media_queries::CSSErrorReporterTest;
+use style::context::QuirksMode;
+use style::parser::{PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES, ParserContext};
+use style::stylesheets::{CssRuleType, Origin};
 use style::values::HasViewportPercentage;
-use style::values::specified::{AbsoluteLength, NoCalcLength, ViewportPercentageLength};
+use style::values::specified::{AbsoluteLength, NoCalcLength, Number, ViewportPercentageLength};
 
 #[test]
 fn length_has_viewport_percentage() {
@@ -13,3 +18,18 @@ fn length_has_viewport_percentage() {
     let l = NoCalcLength::Absolute(AbsoluteLength::Px(Au(100).to_f32_px()));
     assert!(!l.has_viewport_percentage());
 }
+
+#[test]
+fn test_parsing_allo_all_numeric_values() {
+    // In SVG length mode, non-zero lengths are assumed to be px.
+    let url = ::servo_url::ServoUrl::parse("http://localhost").unwrap();
+    let reporter = CSSErrorReporterTest;
+    let context = ParserContext::new(Origin::Author, &url, &reporter,
+                                     Some(CssRuleType::Style), PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES,
+                                     QuirksMode::NoQuirks);
+    let mut parser = Parser::new("-1");
+    let result = Number::parse_non_negative(&context, &mut parser);
+    assert!(result.is_ok());
+    assert_eq!(result.unwrap(), Number::new(-1.));
+}
+