diff --git a/grammar.js b/grammar.js
index e3b4863..938e017 100644
--- a/grammar.js
+++ b/grammar.js
@@ -33,7 +33,7 @@ module.exports = grammar({
 
     star   : $ => "*",
     square : $ => choice('□', '[]'),
-    sort   : $ => choice($.star, $.square, seq($.square, /[0-9]+/)),
+    sort   : $ => choice($.star, $.square, seq($.square, /[0-9₀₁₂₃₄₅₆₇₈₉]+/)),
 
     labs : $ => seq(
       choice('λ', 'fun'),
diff --git a/src/grammar.json b/src/grammar.json
index 4920766..83fa290 100644
--- a/src/grammar.json
+++ b/src/grammar.json
@@ -114,7 +114,7 @@
             },
             {
               "type": "PATTERN",
-              "value": "[0-9]+"
+              "value": "[0-9₀₁₂₃₄₅₆₇₈₉]+"
             }
           ]
         }
diff --git a/src/parser.c b/src/parser.c
index 3a233bd..0db4882 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -555,7 +555,8 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       );
       if (('\t' <= lookahead && lookahead <= '\r') ||
           lookahead == ' ') SKIP(0);
-      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(52);
+      if (('0' <= lookahead && lookahead <= '9') ||
+          (0x2080 <= lookahead && lookahead <= 0x2089)) ADVANCE(52);
       END_STATE();
     case 1:
       if (lookahead == '\n') SKIP(1);
@@ -581,7 +582,8 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       );
       if (('\t' <= lookahead && lookahead <= '\r') ||
           lookahead == ' ') SKIP(2);
-      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(52);
+      if (('0' <= lookahead && lookahead <= '9') ||
+          (0x2080 <= lookahead && lookahead <= 0x2089)) ADVANCE(52);
       if (('A' <= lookahead && lookahead <= 'Z') ||
           lookahead == '_' ||
           ('a' <= lookahead && lookahead <= 'z')) ADVANCE(44);
@@ -596,7 +598,8 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       if (lookahead == 0x25a1) ADVANCE(50);
       if (('\t' <= lookahead && lookahead <= '\r') ||
           lookahead == ' ') SKIP(3);
-      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(52);
+      if (('0' <= lookahead && lookahead <= '9') ||
+          (0x2080 <= lookahead && lookahead <= 0x2089)) ADVANCE(52);
       if (('A' <= lookahead && lookahead <= 'Z') ||
           lookahead == '_' ||
           ('a' <= lookahead && lookahead <= 'z')) ADVANCE(44);
@@ -822,7 +825,8 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       END_STATE();
     case 52:
       ACCEPT_TOKEN(aux_sym_sort_token1);
-      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(52);
+      if (('0' <= lookahead && lookahead <= '9') ||
+          (0x2080 <= lookahead && lookahead <= 0x2089)) ADVANCE(52);
       END_STATE();
     case 53:
       ACCEPT_TOKEN(anon_sym_u03bb);
diff --git a/test/corpus/sorts.txt b/test/corpus/sorts.txt
new file mode 100644
index 0000000..e477404
--- /dev/null
+++ b/test/corpus/sorts.txt
@@ -0,0 +1,72 @@
+=====
+Sorts
+=====
+
+def foo (A : *) (B : □) (C : □₁) (D : []) (E : []1) (F : □1) (G : □₁₂₃) := A;
+
+---
+
+(program
+  (definition
+    (identifier)
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (star)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (param_block
+      (identifier)
+      (expr
+        (app_term
+          (app
+            (term
+              (sort
+                (square)))))))
+    (expr
+      (app_term
+        (app
+          (term
+            (identifier)))))))