diff --git a/blueprintcompiler/language/values.py b/blueprintcompiler/language/values.py
index f92ba67..7430991 100644
--- a/blueprintcompiler/language/values.py
+++ b/blueprintcompiler/language/values.py
@@ -109,9 +109,25 @@ class LiteralValue(Value):
 class Flag(AstNode):
     grammar = UseIdent("value")
 
+    @validate()
+    def validate_for_type(self):
+        type = self.parent.parent.value_type
+        if isinstance(type, gir.Bitfield) and self.tokens["value"] not in type.members:
+            raise CompileError(
+                f"{self.tokens['value']} is not a member of {type.full_name}",
+                did_you_mean=(self.tokens['value'], type.members.keys()),
+            )
+
+
 class FlagsValue(Value):
     grammar = [Flag, "|", Delimited(Flag, "|")]
 
+    @validate()
+    def parent_is_bitfield(self):
+        type = self.parent.value_type
+        if not isinstance(type, gir.Bitfield):
+            raise CompileError(f"{type.full_name} is not a bitfield type")
+
     def emit_xml(self, xml: XmlEmitter):
         xml.put_text("|".join([flag.tokens["value"] for flag in self.children[Flag]]))
 
diff --git a/tests/sample_errors/bitfield_member_dne.blp b/tests/sample_errors/bitfield_member_dne.blp
new file mode 100644
index 0000000..6b4343e
--- /dev/null
+++ b/tests/sample_errors/bitfield_member_dne.blp
@@ -0,0 +1,6 @@
+using Gtk 4.0;
+
+EventControllerScroll {
+  flags: vertical | not_a_value;
+  name: a|b;
+}
diff --git a/tests/sample_errors/bitfield_member_dne.err b/tests/sample_errors/bitfield_member_dne.err
new file mode 100644
index 0000000..28490d5
--- /dev/null
+++ b/tests/sample_errors/bitfield_member_dne.err
@@ -0,0 +1,2 @@
+4,21,11,not_a_value is not a member of Gtk.EventControllerScrollFlags
+5,9,3,string is not a bitfield type
diff --git a/tests/test_samples.py b/tests/test_samples.py
index cb849f1..4c4b17c 100644
--- a/tests/test_samples.py
+++ b/tests/test_samples.py
@@ -155,6 +155,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample_error("action_widget_in_invalid_container")
         self.assert_sample_error("action_widget_response_dne")
         self.assert_sample_error("action_widget_negative_response")
+        self.assert_sample_error("bitfield_member_dne")
         self.assert_sample_error("class_assign")
         self.assert_sample_error("class_dne")
         self.assert_sample_error("consecutive_unexpected_tokens")