diff --git a/scripts/qapi.py b/scripts/qapi.py
index 6ed6a34..c42683b 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -276,6 +276,63 @@ def discriminator_find_enum_define(expr):

     return find_enum(discriminator_type)

+def check_type(expr_info, source, data, allow_array = False,
+               allowed_metas = [], allow_dict = True):
+    global all_names
+
+    if data is None:
+        return
+
+    if data == '**':
+        return
+
+    # Check if array type for data is okay
+    if isinstance(data, list):
+        if not allow_array:
+            raise QAPIExprError(expr_info,
+                                "%s cannot be an array" % source)
+        if len(data) != 1 or not isinstance(data[0], str):
+            raise QAPIExprError(expr_info,
+                                "%s: array type must contain single type name"
+                                % source)
+        data = data[0]
+
+    # Check if type name for data is okay
+    if isinstance(data, str):
+        if not data in all_names:
+            raise QAPIExprError(expr_info,
+                                "%s uses unknown type '%s'"
+                                % (source, data))
+        if not all_names[data] in allowed_metas:
+            raise QAPIExprError(expr_info,
+                                "%s cannot use %s type '%s'"
+                                % (source, all_names[data], data))
+        return
+
+    # data is a dictionary, check that each member is okay
+    if not isinstance(data, OrderedDict):
+        raise QAPIExprError(expr_info,
+                            "%s should be a dictionary" % source)
+    if not allow_dict:
+        raise QAPIExprError(expr_info,
+                            "%s should be a type name" % source)
+    for (key, value) in data.items():
+        check_type(expr_info, "Member '%s' of %s" % (key, source), value,
+                   allow_array=True,
+                   allowed_metas=['built-in', 'union', 'alternate', 'struct',
+                                  'enum'],
+                   allow_dict=True)
+
+def check_command(expr, expr_info):
+    name = expr['command']
+    check_type(expr_info, "'data' for command '%s'" % name,
+               expr.get('data'),
+               allowed_metas=['union', 'struct'])
+    check_type(expr_info, "'returns' for command '%s'" % name,
+               expr.get('returns'), allow_array=True,
+               allowed_metas=['built-in', 'union', 'alternate', 'struct',
+                              'enum'])
+
 def check_event(expr, expr_info):
     global events
     name = expr['event']
@@ -287,7 +344,8 @@ def check_event(expr, expr_info):
         raise QAPIExprError(expr_info, "Event name '%s' should be upper case"
                             % name)
     events.append(name)
-
+    check_type(expr_info, "'data' for event '%s'" % name,
+               expr.get('data'), allowed_metas=['union', 'struct'])
     if params:
         for argname, argentry, optional, structured in parse_args(params):
             if structured:
@@ -348,6 +406,13 @@ def check_union(expr, expr_info):

     # Check every branch
     for (key, value) in members.items():
+        # Each value must name a known type
+        check_type(expr_info, "Member '%s' of union '%s'" % (key, name),
+                   value, allow_array=True,
+                   allowed_metas=['built-in', 'union', 'alternate', 'struct',
+                                  'enum'],
+                   allow_dict=False)
+
         # If the discriminator names an enum type, then all members
         # of 'data' must also be members of the enum type.
         if enum_define:
@@ -383,15 +448,12 @@ def check_alternate(expr, expr_info):
         values[c_key] = key

         # Ensure alternates have no type conflicts.
-        if isinstance(value, list):
-            raise QAPIExprError(expr_info,
-                                "Alternate '%s' member '%s' must "
-                                "not be array type" % (name, key))
+        check_type(expr_info, "Member '%s' of alternate '%s'" % (key, name),
+                   value,
+                   allowed_metas=['built-in', 'union', 'struct', 'enum'],
+                   allow_dict=False)
         qtype = find_alternate_member_qtype(value)
-        if not qtype:
-            raise QAPIExprError(expr_info,
-                                "Alternate '%s' member '%s' has "
-                                "invalid type '%s'" % (name, key, value))
+        assert qtype
         if qtype in types_seen:
             raise QAPIExprError(expr_info,
                                 "Alternate '%s' member '%s' has "
@@ -419,6 +481,14 @@ def check_enum(expr, expr_info):
                                 % (name, member, values[key]))
         values[key] = member

+def check_struct(expr, expr_info):
+    name = expr['type']
+    members = expr['data']
+
+    check_type(expr_info, "'data' for type '%s'" % name, members)
+    check_type(expr_info, "'base' for type '%s'" % name, expr.get('base'),
+               allowed_metas=['struct'], allow_dict=False)
+
 def check_exprs(schema):
     for expr_elem in schema.exprs:
         expr = expr_elem['expr']
@@ -430,8 +500,14 @@ def check_exprs(schema):
             check_union(expr, info)
         elif expr.has_key('alternate'):
             check_alternate(expr, info)
+        elif expr.has_key('type'):
+            check_struct(expr, info)
+        elif expr.has_key('command'):
+            check_command(expr, info)
         elif expr.has_key('event'):
             check_event(expr, info)
+        else:
+            assert False, 'unexpected meta type'

 def check_keys(expr_elem, meta, required, optional=[]):
     expr = expr_elem['expr']
diff --git a/tests/qapi-schema/alternate-array.err b/tests/qapi-schema/alternate-array.err
index 5721ed2..f4f0c1d 100644
--- a/tests/qapi-schema/alternate-array.err
+++ b/tests/qapi-schema/alternate-array.err
@@ -1 +1 @@
-tests/qapi-schema/alternate-array.json:4: Alternate 'Alt' member 'two' must not be array type
+tests/qapi-schema/alternate-array.json:4: Member 'two' of alternate 'Alt' cannot be an array
diff --git a/tests/qapi-schema/alternate-nested.err b/tests/qapi-schema/alternate-nested.err
index 00b05c6..4d1187e 100644
--- a/tests/qapi-schema/alternate-nested.err
+++ b/tests/qapi-schema/alternate-nested.err
@@ -1 +1 @@
-tests/qapi-schema/alternate-nested.json:4: Alternate 'Alt2' member 'nested' has invalid type 'Alt1'
+tests/qapi-schema/alternate-nested.json:4: Member 'nested' of alternate 'Alt2' cannot use alternate type 'Alt1'
diff --git a/tests/qapi-schema/alternate-unknown.err b/tests/qapi-schema/alternate-unknown.err
index 7af1b4c..dea45dc 100644
--- a/tests/qapi-schema/alternate-unknown.err
+++ b/tests/qapi-schema/alternate-unknown.err
@@ -1 +1 @@
-tests/qapi-schema/alternate-unknown.json:2: Alternate 'Alt' member 'unknown' has invalid type 'MissingType'
+tests/qapi-schema/alternate-unknown.json:2: Member 'unknown' of alternate 'Alt' uses unknown type 'MissingType'
diff --git a/tests/qapi-schema/bad-base.err b/tests/qapi-schema/bad-base.err
index e69de29..f398bbb 100644
--- a/tests/qapi-schema/bad-base.err
+++ b/tests/qapi-schema/bad-base.err
@@ -0,0 +1 @@
+tests/qapi-schema/bad-base.json:3: 'base' for type 'MyType' cannot use union type 'Union'
diff --git a/tests/qapi-schema/bad-base.exit b/tests/qapi-schema/bad-base.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/bad-base.exit
+++ b/tests/qapi-schema/bad-base.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/bad-base.json b/tests/qapi-schema/bad-base.json
index de964a0..a690470 100644
--- a/tests/qapi-schema/bad-base.json
+++ b/tests/qapi-schema/bad-base.json
@@ -1,3 +1,3 @@
-# FIXME: we should reject a base that is not a struct
+# we reject a base that is not a struct
 { 'union': 'Union', 'data': { 'a': 'int', 'b': 'str' } }
 { 'type': 'MyType', 'base': 'Union', 'data': { 'c': 'int' } }
diff --git a/tests/qapi-schema/bad-base.out b/tests/qapi-schema/bad-base.out
index 91d12fc..e69de29 100644
--- a/tests/qapi-schema/bad-base.out
+++ b/tests/qapi-schema/bad-base.out
@@ -1,4 +0,0 @@
-[OrderedDict([('union', 'Union'), ('data', OrderedDict([('a', 'int'), ('b', 'str')]))]),
- OrderedDict([('type', 'MyType'), ('base', 'Union'), ('data', OrderedDict([('c', 'int')]))])]
-[{'enum_name': 'UnionKind', 'enum_values': None}]
-[OrderedDict([('type', 'MyType'), ('base', 'Union'), ('data', OrderedDict([('c', 'int')]))])]
diff --git a/tests/qapi-schema/data-array-empty.err b/tests/qapi-schema/data-array-empty.err
index e69de29..f713f14 100644
--- a/tests/qapi-schema/data-array-empty.err
+++ b/tests/qapi-schema/data-array-empty.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-array-empty.json:2: Member 'empty' of 'data' for command 'oops': array type must contain single type name
diff --git a/tests/qapi-schema/data-array-empty.exit b/tests/qapi-schema/data-array-empty.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-array-empty.exit
+++ b/tests/qapi-schema/data-array-empty.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-array-empty.json b/tests/qapi-schema/data-array-empty.json
index edb543a..652dcfb 100644
--- a/tests/qapi-schema/data-array-empty.json
+++ b/tests/qapi-schema/data-array-empty.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an array for data if it does not contain a known type
+# we reject an array for data if it does not contain a known type
 { 'command': 'oops', 'data': { 'empty': [ ] } }
diff --git a/tests/qapi-schema/data-array-empty.out b/tests/qapi-schema/data-array-empty.out
index 6f25c9e..e69de29 100644
--- a/tests/qapi-schema/data-array-empty.out
+++ b/tests/qapi-schema/data-array-empty.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', OrderedDict([('empty', [])]))])]
-[]
-[]
diff --git a/tests/qapi-schema/data-array-unknown.err b/tests/qapi-schema/data-array-unknown.err
index e69de29..21c39ca 100644
--- a/tests/qapi-schema/data-array-unknown.err
+++ b/tests/qapi-schema/data-array-unknown.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-array-unknown.json:2: Member 'array' of 'data' for command 'oops' uses unknown type 'NoSuchType'
diff --git a/tests/qapi-schema/data-array-unknown.exit b/tests/qapi-schema/data-array-unknown.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-array-unknown.exit
+++ b/tests/qapi-schema/data-array-unknown.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-array-unknown.json b/tests/qapi-schema/data-array-unknown.json
index 20cd3c0..6f3e883 100644
--- a/tests/qapi-schema/data-array-unknown.json
+++ b/tests/qapi-schema/data-array-unknown.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an array for data if it does not contain a known type
+# we reject an array for data if it does not contain a known type
 { 'command': 'oops', 'data': { 'array': [ 'NoSuchType' ] } }
diff --git a/tests/qapi-schema/data-array-unknown.out b/tests/qapi-schema/data-array-unknown.out
index 4314ab5..e69de29 100644
--- a/tests/qapi-schema/data-array-unknown.out
+++ b/tests/qapi-schema/data-array-unknown.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', OrderedDict([('array', ['NoSuchType'])]))])]
-[]
-[]
diff --git a/tests/qapi-schema/data-int.err b/tests/qapi-schema/data-int.err
index e69de29..1a9b077 100644
--- a/tests/qapi-schema/data-int.err
+++ b/tests/qapi-schema/data-int.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-int.json:2: 'data' for command 'oops' cannot use built-in type 'int'
diff --git a/tests/qapi-schema/data-int.exit b/tests/qapi-schema/data-int.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-int.exit
+++ b/tests/qapi-schema/data-int.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-int.json b/tests/qapi-schema/data-int.json
index 37916e0..a334d92 100644
--- a/tests/qapi-schema/data-int.json
+++ b/tests/qapi-schema/data-int.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject commands where data is not an array or complex type
+# we reject commands where data is not an array or complex type
 { 'command': 'oops', 'data': 'int' }
diff --git a/tests/qapi-schema/data-int.out b/tests/qapi-schema/data-int.out
index e589a4f..e69de29 100644
--- a/tests/qapi-schema/data-int.out
+++ b/tests/qapi-schema/data-int.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', 'int')])]
-[]
-[]
diff --git a/tests/qapi-schema/data-member-array-bad.err b/tests/qapi-schema/data-member-array-bad.err
index e69de29..2c072d5 100644
--- a/tests/qapi-schema/data-member-array-bad.err
+++ b/tests/qapi-schema/data-member-array-bad.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-member-array-bad.json:2: Member 'member' of 'data' for command 'oops': array type must contain single type name
diff --git a/tests/qapi-schema/data-member-array-bad.exit b/tests/qapi-schema/data-member-array-bad.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-member-array-bad.exit
+++ b/tests/qapi-schema/data-member-array-bad.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-member-array-bad.json b/tests/qapi-schema/data-member-array-bad.json
index c954af1..b2ff144 100644
--- a/tests/qapi-schema/data-member-array-bad.json
+++ b/tests/qapi-schema/data-member-array-bad.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject data if it does not contain a valid array type
+# we reject data if it does not contain a valid array type
 { 'command': 'oops', 'data': { 'member': [ { 'nested': 'str' } ] } }
diff --git a/tests/qapi-schema/data-member-array-bad.out b/tests/qapi-schema/data-member-array-bad.out
index 0e00c41..e69de29 100644
--- a/tests/qapi-schema/data-member-array-bad.out
+++ b/tests/qapi-schema/data-member-array-bad.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', OrderedDict([('member', [OrderedDict([('nested', 'str')])])]))])]
-[]
-[]
diff --git a/tests/qapi-schema/data-member-unknown.err b/tests/qapi-schema/data-member-unknown.err
index e69de29..ab905db 100644
--- a/tests/qapi-schema/data-member-unknown.err
+++ b/tests/qapi-schema/data-member-unknown.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-member-unknown.json:2: Member 'member' of 'data' for command 'oops' uses unknown type 'NoSuchType'
diff --git a/tests/qapi-schema/data-member-unknown.exit b/tests/qapi-schema/data-member-unknown.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-member-unknown.exit
+++ b/tests/qapi-schema/data-member-unknown.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-member-unknown.json b/tests/qapi-schema/data-member-unknown.json
index 40e6252..342a41e 100644
--- a/tests/qapi-schema/data-member-unknown.json
+++ b/tests/qapi-schema/data-member-unknown.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject data if it does not contain a known type
+# we reject data if it does not contain a known type
 { 'command': 'oops', 'data': { 'member': 'NoSuchType' } }
diff --git a/tests/qapi-schema/data-member-unknown.out b/tests/qapi-schema/data-member-unknown.out
index 36252a5..e69de29 100644
--- a/tests/qapi-schema/data-member-unknown.out
+++ b/tests/qapi-schema/data-member-unknown.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', OrderedDict([('member', 'NoSuchType')]))])]
-[]
-[]
diff --git a/tests/qapi-schema/data-unknown.err b/tests/qapi-schema/data-unknown.err
index e69de29..5b07277 100644
--- a/tests/qapi-schema/data-unknown.err
+++ b/tests/qapi-schema/data-unknown.err
@@ -0,0 +1 @@
+tests/qapi-schema/data-unknown.json:2: 'data' for command 'oops' uses unknown type 'NoSuchType'
diff --git a/tests/qapi-schema/data-unknown.exit b/tests/qapi-schema/data-unknown.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/data-unknown.exit
+++ b/tests/qapi-schema/data-unknown.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/data-unknown.json b/tests/qapi-schema/data-unknown.json
index 776bd34..32aba43 100644
--- a/tests/qapi-schema/data-unknown.json
+++ b/tests/qapi-schema/data-unknown.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject data if it does not contain a known type
+# we reject data if it does not contain a known type
 { 'command': 'oops', 'data': 'NoSuchType' }
diff --git a/tests/qapi-schema/data-unknown.out b/tests/qapi-schema/data-unknown.out
index 2c60726..e69de29 100644
--- a/tests/qapi-schema/data-unknown.out
+++ b/tests/qapi-schema/data-unknown.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('data', 'NoSuchType')])]
-[]
-[]
diff --git a/tests/qapi-schema/returns-array-bad.err b/tests/qapi-schema/returns-array-bad.err
index e69de29..138095c 100644
--- a/tests/qapi-schema/returns-array-bad.err
+++ b/tests/qapi-schema/returns-array-bad.err
@@ -0,0 +1 @@
+tests/qapi-schema/returns-array-bad.json:2: 'returns' for command 'oops': array type must contain single type name
diff --git a/tests/qapi-schema/returns-array-bad.exit b/tests/qapi-schema/returns-array-bad.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/returns-array-bad.exit
+++ b/tests/qapi-schema/returns-array-bad.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/returns-array-bad.json b/tests/qapi-schema/returns-array-bad.json
index 14882c1..09b0b1f 100644
--- a/tests/qapi-schema/returns-array-bad.json
+++ b/tests/qapi-schema/returns-array-bad.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an array return that is not a single type
+# we reject an array return that is not a single type
 { 'command': 'oops', 'returns': [ 'str', 'str' ] }
diff --git a/tests/qapi-schema/returns-array-bad.out b/tests/qapi-schema/returns-array-bad.out
index eccad55..e69de29 100644
--- a/tests/qapi-schema/returns-array-bad.out
+++ b/tests/qapi-schema/returns-array-bad.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('returns', ['str', 'str'])])]
-[]
-[]
diff --git a/tests/qapi-schema/returns-unknown.err b/tests/qapi-schema/returns-unknown.err
index e69de29..1f43e3a 100644
--- a/tests/qapi-schema/returns-unknown.err
+++ b/tests/qapi-schema/returns-unknown.err
@@ -0,0 +1 @@
+tests/qapi-schema/returns-unknown.json:2: 'returns' for command 'oops' uses unknown type 'NoSuchType'
diff --git a/tests/qapi-schema/returns-unknown.exit b/tests/qapi-schema/returns-unknown.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/returns-unknown.exit
+++ b/tests/qapi-schema/returns-unknown.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/returns-unknown.json b/tests/qapi-schema/returns-unknown.json
index 61f20eb..25bd498 100644
--- a/tests/qapi-schema/returns-unknown.json
+++ b/tests/qapi-schema/returns-unknown.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject returns if it does not contain a known type
+# we reject returns if it does not contain a known type
 { 'command': 'oops', 'returns': 'NoSuchType' }
diff --git a/tests/qapi-schema/returns-unknown.out b/tests/qapi-schema/returns-unknown.out
index a482c83..e69de29 100644
--- a/tests/qapi-schema/returns-unknown.out
+++ b/tests/qapi-schema/returns-unknown.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'oops'), ('returns', 'NoSuchType')])]
-[]
-[]
diff --git a/tests/qapi-schema/union-unknown.err b/tests/qapi-schema/union-unknown.err
index e69de29..54fe456 100644
--- a/tests/qapi-schema/union-unknown.err
+++ b/tests/qapi-schema/union-unknown.err
@@ -0,0 +1 @@
+tests/qapi-schema/union-unknown.json:2: Member 'unknown' of union 'Union' uses unknown type 'MissingType'
diff --git a/tests/qapi-schema/union-unknown.exit b/tests/qapi-schema/union-unknown.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/union-unknown.exit
+++ b/tests/qapi-schema/union-unknown.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/union-unknown.json b/tests/qapi-schema/union-unknown.json
index 258f1d3..aa7e814 100644
--- a/tests/qapi-schema/union-unknown.json
+++ b/tests/qapi-schema/union-unknown.json
@@ -1,3 +1,3 @@
-# FIXME: we should reject a union with unknown type in branch
+# we reject a union with unknown type in branch
 { 'union': 'Union',
   'data': { 'unknown': 'MissingType' } }
diff --git a/tests/qapi-schema/union-unknown.out b/tests/qapi-schema/union-unknown.out
index 8223dcf..e69de29 100644
--- a/tests/qapi-schema/union-unknown.out
+++ b/tests/qapi-schema/union-unknown.out
@@ -1,3 +0,0 @@
-[OrderedDict([('union', 'Union'), ('data', OrderedDict([('unknown', 'MissingType')]))])]
-[{'enum_name': 'UnionKind', 'enum_values': None}]
-[]
