diff --git a/src/rosbags/typesys/msg.py b/src/rosbags/typesys/msg.py
index 71e5f20a..5ee4df97 100644
--- a/src/rosbags/typesys/msg.py
+++ b/src/rosbags/typesys/msg.py
@@ -45,7 +45,9 @@ comment
 
 const_dcl
   = 'string' identifier r'=(?!={79}\n)' r'[^\n]+'
+  / type_spec identifier '=' float_literal
   / type_spec identifier '=' integer_literal
+  / type_spec identifier '=' boolean_literal
 
 field_dcl
   = type_spec identifier default_value?
@@ -82,15 +84,17 @@ default_value
   = literal
 
 literal
-  = boolean_literal
-  / float_literal
+  = float_literal
   / integer_literal
+  / boolean_literal
   / string_literal
   / array_literal
 
 boolean_literal
-  = 'true'
-  / 'false'
+  = r'[tT][rR][uU][eE]'
+  / r'[fF][aA][lL][sS][eE]'
+  / '0'
+  / '1'
 
 integer_literal
   = hexadecimal_literal
@@ -283,7 +287,7 @@ class VisitorMSG(Visitor):
 
     def visit_boolean_literal(self, children: Any) -> Any:
         """Process boolean literal."""
-        return children[1] == 'TRUE'
+        return children.lower() in ['true', '1']
 
     def visit_float_literal(self, children: Any) -> Any:
         """Process float literal."""
diff --git a/tests/test_parse.py b/tests/test_parse.py
index edce9ab7..dc552975 100644
--- a/tests/test_parse.py
+++ b/tests/test_parse.py
@@ -17,7 +17,9 @@ from rosbags.typesys.types import FIELDDEFS
 MSG = """
 # comment
 
+bool b=true
 int32 global=42
+float32 f=1.33
 string str= foo bar\t
 
 std_msgs/Header header
@@ -195,7 +197,12 @@ def test_parse_msg() -> None:
     ret = get_types_from_msg(MSG, 'test_msgs/msg/Foo')
     assert 'test_msgs/msg/Foo' in ret
     consts, fields = ret['test_msgs/msg/Foo']
-    assert consts == [('global', 'int32', 42), ('str', 'string', 'foo bar')]
+    assert consts == [
+        ('b', 'bool', True),
+        ('global', 'int32', 42),
+        ('f', 'float32', 1.33),
+        ('str', 'string', 'foo bar'),
+    ]
     assert fields[0][0] == 'header'
     assert fields[0][1][1] == 'std_msgs/msg/Header'
     assert fields[1][0] == 'bool'