diff --git a/convert.go b/convert.go
index a153788..507f7eb 100644
--- a/convert.go
+++ b/convert.go
@@ -184,6 +184,7 @@ var subscripts = map[rune]rune{
 	'\u0038': '\u2088',
 	'\u0039': '\u2089',
 	'\u002b': '\u208a',
+	'\u002d': '\u208b',
 	'\u2212': '\u208b',
 	'\u003d': '\u208c',
 	'\u0028': '\u208d',