diff --git a/grammar.js b/grammar.js
index 5312f8b..45d59b2 100644
--- a/grammar.js
+++ b/grammar.js
@@ -219,7 +219,7 @@ module.exports = grammar({
     //   [+U]uNonSurrogate
     //   [~U]uHex4Digits
     //   [+U]u{CodePoint}
-    group_name: _ => /[A-Za-z0-9]+/,
+    group_name: _ => /[A-Za-z_][A-Za-z0-9_]*/,
 
     decimal_digits: _ => /\d+/,
   },
diff --git a/src/grammar.json b/src/grammar.json
index 28ced0a..2ddcffb 100644
--- a/src/grammar.json
+++ b/src/grammar.json
@@ -743,7 +743,7 @@
     },
     "group_name": {
       "type": "PATTERN",
-      "value": "[A-Za-z0-9]+"
+      "value": "[A-Za-z_][A-Za-z0-9_]*"
     },
     "decimal_digits": {
       "type": "PATTERN",
diff --git a/src/parser.c b/src/parser.c
index 8aea575..f9d660d 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -683,8 +683,9 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       if (lookahead == '=') ADVANCE(36);
       if (lookahead == '>') ADVANCE(54);
       if (lookahead == '}') ADVANCE(61);
-      if (('0' <= lookahead && lookahead <= '9') ||
-          ('A' <= lookahead && lookahead <= 'Z') ||
+      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(75);
+      if (('A' <= lookahead && lookahead <= 'Z') ||
+          lookahead == '_' ||
           ('a' <= lookahead && lookahead <= 'z')) ADVANCE(74);
       END_STATE();
     case 5:
@@ -704,7 +705,6 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
     case 8:
       if (lookahead == '\n') SKIP(8);
       if (lookahead == '\r') SKIP(7);
-      if (('0' <= lookahead && lookahead <= '9')) ADVANCE(75);
       if (('A' <= lookahead && lookahead <= 'Z') ||
           ('a' <= lookahead && lookahead <= 'z')) ADVANCE(46);
       END_STATE();
@@ -1062,6 +1062,7 @@ static bool ts_lex(TSLexer *lexer, TSStateId state) {
       ACCEPT_TOKEN(sym_group_name);
       if (('0' <= lookahead && lookahead <= '9') ||
           ('A' <= lookahead && lookahead <= 'Z') ||
+          lookahead == '_' ||
           ('a' <= lookahead && lookahead <= 'z')) ADVANCE(74);
       END_STATE();
     case 75:
@@ -1150,9 +1151,9 @@ static const TSLexMode ts_lex_modes[STATE_COUNT] = {
   [73] = {.lex_state = 0},
   [74] = {.lex_state = 4},
   [75] = {.lex_state = 4},
-  [76] = {.lex_state = 8},
+  [76] = {.lex_state = 4},
   [77] = {.lex_state = 0},
-  [78] = {.lex_state = 8},
+  [78] = {.lex_state = 4},
   [79] = {.lex_state = 0},
   [80] = {.lex_state = 0},
   [81] = {.lex_state = 8},
diff --git a/test/corpus/main.txt b/test/corpus/main.txt
index 55e72a2..e2e5d09 100644
--- a/test/corpus/main.txt
+++ b/test/corpus/main.txt
@@ -452,7 +452,7 @@ hello (.*)
 ================================================================================
 named capturing groups
 ================================================================================
-(?<world>.*)
+(?<the_world>.*)
 --------------------------------------------------------------------------------
 
 (pattern
@@ -467,7 +467,7 @@ named capturing groups
 ================================================================================
 named capturing groups - backreferences
 ================================================================================
-(?<world>.*)\kworld
+(?<the_world>.*)\kthe_world
 --------------------------------------------------------------------------------
 
 (pattern