diff --git a/components/style/gecko_string_cache/mod.rs b/components/style/gecko_string_cache/mod.rs
index 297599e2080..b0c8750265b 100644
--- a/components/style/gecko_string_cache/mod.rs
+++ b/components/style/gecko_string_cache/mod.rs
@@ -122,7 +122,8 @@ impl WeakAtom {
             unsafe { u8_ptr.offset(string_offset) as *const u16 }
         } else {
             let atom_ptr = self.as_ptr() as *const nsDynamicAtom;
-            unsafe { (*(atom_ptr)).mString }
+            // Dynamic atom chars are stored at the end of the object.
+            unsafe { atom_ptr.offset(1) as *const u16 }
         };
         unsafe { slice::from_raw_parts(string, self.len() as usize) }
     }