diff --git a/Lib/fontTools/feaLib/parser.py b/Lib/fontTools/feaLib/parser.py
index 6020b158ff..39feac2d85 100644
--- a/Lib/fontTools/feaLib/parser.py
+++ b/Lib/fontTools/feaLib/parser.py
@@ -416,6 +416,11 @@ def parse_glyphclass_(self, accept_glyphname, accept_null=False):
                     self.next_token_location_,
                 )
         self.expect_symbol_("]")
+        if not glyphs.glyphSet():
+            raise FeatureLibError(
+                    "Glyph class cannot be empty",
+                    self.cur_token_location_,
+                )
         return glyphs
 
     def parse_glyph_pattern_(self, vertical):