diff --git a/font-patcher b/font-patcher
index a24e706e6..03595822d 100755
--- a/font-patcher
+++ b/font-patcher
@@ -6,7 +6,7 @@
 from __future__ import absolute_import, print_function, unicode_literals
 
 # Change the script version when you edit this script:
-script_version = "3.5.0"
+script_version = "3.5.1"
 
 version = "2.3.0"
 projectName = "Nerd Fonts"
@@ -915,17 +915,24 @@ class font_patcher:
     def add_glyphrefs_to_essential(self, unicode):
         self.essential.add(unicode)
         # According to fontforge spec, altuni is either None or a tuple of tuples
-        if self.sourceFont[unicode].altuni is not None:
-            for r in self.sourceFont[unicode].altuni:
+        # Those tuples contained in altuni are of the following "format":
+        # (unicode-value, variation-selector, reserved-field)
+        altuni = self.sourceFont[unicode].altuni
+        if altuni is not None:
+            for altcode in [ v for v, s, r in altuni if v >= 0 ]:
                 # If alternate unicode already exists in self.essential,
                 # that means it has gone through this function before.
                 # Therefore we skip it to avoid infinite loop.
                 # A unicode value of -1 basically means unused and is also worth skipping.
-                if r[0] not in self.essential and r[0] >= 0:
-                    self.add_glyphrefs_to_essential(r[0])
-        for r in self.sourceFont[unicode].references:
-            if self.sourceFont[r[0]].unicode not in self.essential and self.sourceFont[r[0]].unicode >= 0:
-                self.add_glyphrefs_to_essential(self.sourceFont[r[0]].unicode)
+                if altcode not in self.essential:
+                    self.add_glyphrefs_to_essential(altcode)
+        # From fontforge documentation:
+        # glyph.references return a tuple of tuples containing, for each reference in foreground,
+        # a glyph name, a transformation matrix, and whether the reference is currently selected.
+        references = self.sourceFont[unicode].references
+        for refcode in [ self.sourceFont[n].unicode for n, m, s in references ]:
+            if refcode not in self.essential and refcode >= 0:
+                self.add_glyphrefs_to_essential(refcode)
 
     def get_essential_references(self):
         """Find glyphs that are needed for the basic glyphs"""