diff --git a/components/style/gecko_bindings/bindings.rs b/components/style/gecko_bindings/bindings.rs
index 1d5a0909913..36075707b5b 100644
--- a/components/style/gecko_bindings/bindings.rs
+++ b/components/style/gecko_bindings/bindings.rs
@@ -1074,6 +1074,10 @@ extern "C" {
     pub fn Gecko_CSSValue_GetAbsoluteLength(css_value: nsCSSValueBorrowed)
      -> nscoord;
 }
+extern "C" {
+    pub fn Gecko_GetAppUnitsPerPhysicalInch(pres_context: RawGeckoPresContextBorrowed)
+     -> i32;
+}
 extern "C" {
     pub fn Gecko_CSSValue_GetKeyword(aCSSValue: nsCSSValueBorrowed)
      -> nsCSSKeyword;