diff --git a/src/core/format_spec/lexer.py b/src/core/format_spec/lexer.py
index 578aa51..70696f9 100644
--- a/src/core/format_spec/lexer.py
+++ b/src/core/format_spec/lexer.py
@@ -116,5 +116,5 @@ class FormatSpecLexer:
         while self.peek().isdigit():
             self.advance()
 
-        value: float = float(self.source[self.start:self.idx])
+        value: int = int(self.source[self.start:self.idx])
         self.add_token(TokenType.NUMBER, value)
diff --git a/src/core/format_spec/parser.py b/src/core/format_spec/parser.py
index 7ad7eba..a1084b2 100644
--- a/src/core/format_spec/parser.py
+++ b/src/core/format_spec/parser.py
@@ -94,7 +94,7 @@ class FormatSpecParser:
         if self.match(TokenType.NUMBER):
             width = self.previous().value
         if self.match(TokenType.COMMA, TokenType.UNDERSCORE):
-            grouping = self.previous().value
+            grouping = self.previous()
         return FormatSpecIntegral(
             width=width,
             grouping=grouping
@@ -107,7 +107,7 @@ class FormatSpecParser:
             if self.match(TokenType.NUMBER):
                 precision = self.previous().value
             if self.match(TokenType.COMMA, TokenType.UNDERSCORE):
-                grouping = self.previous().value
+                grouping = self.previous()
         return FormatSpecDecimal(
             precision=precision,
             grouping=grouping