diff --git a/components/gfx/text/glyph.rs b/components/gfx/text/glyph.rs
index 73a66ff19bf..ea5a009959e 100644
--- a/components/gfx/text/glyph.rs
+++ b/components/gfx/text/glyph.rs
@@ -254,10 +254,10 @@ impl<'a> DetailedGlyphStore {
 
         let i = self.detail_lookup.binary_search(&key)
             .expect("Invalid index not found in detailed glyph lookup table!");
-
-        assert!(i + (count as usize) <= self.detail_buffer.len());
+        let main_detail_offset = self.detail_lookup[i].detail_offset;
+        assert!(main_detail_offset + (count as usize) <= self.detail_buffer.len());
         // return a slice into the buffer
-        &self.detail_buffer[i .. i + count as usize]
+        &self.detail_buffer[main_detail_offset .. main_detail_offset + count as usize]
     }
 
     fn detailed_glyph_with_index(&'a self,
@@ -274,9 +274,9 @@ impl<'a> DetailedGlyphStore {
 
         let i = self.detail_lookup.binary_search(&key)
             .expect("Invalid index not found in detailed glyph lookup table!");
-
-        assert!(i + (detail_offset as usize) < self.detail_buffer.len());
-        &self.detail_buffer[i + (detail_offset as usize)]
+        let main_detail_offset = self.detail_lookup[i].detail_offset;
+        assert!(main_detail_offset + (detail_offset as usize) < self.detail_buffer.len());
+        &self.detail_buffer[main_detail_offset + (detail_offset as usize)]
     }
 
     fn ensure_sorted(&mut self) {
diff --git a/tests/wpt/metadata-css/css-text-3_dev/html/word-break-break-all-007.htm.ini b/tests/wpt/metadata-css/css-text-3_dev/html/word-break-break-all-007.htm.ini
deleted file mode 100644
index b2b3212943b..00000000000
--- a/tests/wpt/metadata-css/css-text-3_dev/html/word-break-break-all-007.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[word-break-break-all-007.htm]
-  type: reftest
-  expected: FAIL