diff --git a/scripts/qapi.py b/scripts/qapi.py
index 85aa8bf..8fbc45f 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -348,7 +348,29 @@ def check_exprs(schema):
         if expr.has_key('enum'):
             check_enum(expr, info)

+def check_keys(expr_elem, meta, required, optional=[]):
+    expr = expr_elem['expr']
+    info = expr_elem['info']
+    name = expr[meta]
+    if not isinstance(name, basestring):
+        raise QAPIExprError(info,
+                            "%s key must have a string value" % meta)
+    expr_elem['name'] = name
+    required.append(meta)
+    for (key, value) in expr.items():
+        if not key in required and not key in optional:
+            raise QAPIExprError(info,
+                                "%s '%s' has unknown key '%s'"
+                                % (meta, name, key))
+    for key in required:
+        if not expr.has_key(key):
+            raise QAPIExprError(info,
+                                "%s '%s' is missing key '%s'"
+                                % (meta, name, key))
+
+
 def parse_schema(input_file):
+    # First pass: read entire file into memory
     try:
         schema = QAPISchema(open(input_file, "r"))
     except (QAPISchemaError, QAPIExprError), e:
@@ -357,24 +379,44 @@ def parse_schema(input_file):

     exprs = []

-    for expr_elem in schema.exprs:
-        expr = expr_elem['expr']
-        if expr.has_key('enum'):
-            add_enum(expr['enum'], expr.get('data'))
-        elif expr.has_key('union'):
-            add_union(expr)
-        elif expr.has_key('type'):
-            add_struct(expr)
-        exprs.append(expr)
-
-    # Try again for hidden UnionKind enum
-    for expr_elem in schema.exprs:
-        expr = expr_elem['expr']
-        if expr.has_key('union'):
-            if not discriminator_find_enum_define(expr):
-                add_enum('%sKind' % expr['union'])
-
     try:
+        # Next pass: learn the types and check for valid expression keys. At
+        # this point, top-level 'include' has already been flattened.
+        for expr_elem in schema.exprs:
+            expr = expr_elem['expr']
+            if expr.has_key('enum'):
+                check_keys(expr_elem, 'enum', ['data'])
+                add_enum(expr['enum'], expr['data'])
+            elif expr.has_key('union'):
+                # Two styles of union, based on discriminator
+                discriminator = expr.get('discriminator')
+                if discriminator == {}:
+                    check_keys(expr_elem, 'union', ['data', 'discriminator'])
+                else:
+                    check_keys(expr_elem, 'union', ['data'],
+                               ['base', 'discriminator'])
+                add_union(expr)
+            elif expr.has_key('type'):
+                check_keys(expr_elem, 'type', ['data'], ['base'])
+                add_struct(expr)
+            elif expr.has_key('command'):
+                check_keys(expr_elem, 'command', [],
+                           ['data', 'returns', 'gen', 'success-response'])
+            elif expr.has_key('event'):
+                check_keys(expr_elem, 'event', [], ['data'])
+            else:
+                raise QAPIExprError(expr_elem['info'],
+                                    "expression is missing metatype")
+            exprs.append(expr)
+
+        # Try again for hidden UnionKind enum
+        for expr_elem in schema.exprs:
+            expr = expr_elem['expr']
+            if expr.has_key('union'):
+                if not discriminator_find_enum_define(expr):
+                    add_enum('%sKind' % expr['union'])
+
+        # Final pass - validate that exprs make sense
         check_exprs(schema)
     except QAPIExprError, e:
         print >>sys.stderr, e
diff --git a/tests/qapi-schema/bad-type-dict.err b/tests/qapi-schema/bad-type-dict.err
index e69de29..b7c73cc 100644
--- a/tests/qapi-schema/bad-type-dict.err
+++ b/tests/qapi-schema/bad-type-dict.err
@@ -0,0 +1 @@
+tests/qapi-schema/bad-type-dict.json:2: command key must have a string value
diff --git a/tests/qapi-schema/bad-type-dict.exit b/tests/qapi-schema/bad-type-dict.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/bad-type-dict.exit
+++ b/tests/qapi-schema/bad-type-dict.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/bad-type-dict.json b/tests/qapi-schema/bad-type-dict.json
index 3c392a7..2a91b24 100644
--- a/tests/qapi-schema/bad-type-dict.json
+++ b/tests/qapi-schema/bad-type-dict.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an expression with a metatype that is not a string
+# we reject an expression with a metatype that is not a string
 { 'command': { } }
diff --git a/tests/qapi-schema/bad-type-dict.out b/tests/qapi-schema/bad-type-dict.out
index c62f1ed..e69de29 100644
--- a/tests/qapi-schema/bad-type-dict.out
+++ b/tests/qapi-schema/bad-type-dict.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', OrderedDict())])]
-[]
-[]
diff --git a/tests/qapi-schema/double-type.err b/tests/qapi-schema/double-type.err
index e69de29..394127b 100644
--- a/tests/qapi-schema/double-type.err
+++ b/tests/qapi-schema/double-type.err
@@ -0,0 +1 @@
+tests/qapi-schema/double-type.json:2: type 'bar' has unknown key 'command'
diff --git a/tests/qapi-schema/double-type.exit b/tests/qapi-schema/double-type.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/double-type.exit
+++ b/tests/qapi-schema/double-type.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/double-type.json b/tests/qapi-schema/double-type.json
index 6ca96b9..471623a 100644
--- a/tests/qapi-schema/double-type.json
+++ b/tests/qapi-schema/double-type.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an expression with ambiguous metatype
+# we reject an expression with ambiguous metatype
 { 'command': 'foo', 'type': 'bar', 'data': { } }
diff --git a/tests/qapi-schema/double-type.out b/tests/qapi-schema/double-type.out
index 3e244f5..e69de29 100644
--- a/tests/qapi-schema/double-type.out
+++ b/tests/qapi-schema/double-type.out
@@ -1,3 +0,0 @@
-[OrderedDict([('command', 'foo'), ('type', 'bar'), ('data', OrderedDict())])]
-[]
-[OrderedDict([('command', 'foo'), ('type', 'bar'), ('data', OrderedDict())])]
diff --git a/tests/qapi-schema/enum-missing-data.err b/tests/qapi-schema/enum-missing-data.err
index 4b8b59e..62f4a7f 100644
--- a/tests/qapi-schema/enum-missing-data.err
+++ b/tests/qapi-schema/enum-missing-data.err
@@ -1 +1 @@
-tests/qapi-schema/enum-missing-data.json:2: enum 'MyEnum' requires an array for 'data'
+tests/qapi-schema/enum-missing-data.json:2: enum 'MyEnum' is missing key 'data'
diff --git a/tests/qapi-schema/indented-expr.json b/tests/qapi-schema/indented-expr.json
index d80af60..7115d31 100644
--- a/tests/qapi-schema/indented-expr.json
+++ b/tests/qapi-schema/indented-expr.json
@@ -1,2 +1,2 @@
-{ 'id' : 'eins' }
- { 'id' : 'zwei' }
+{ 'command' : 'eins' }
+ { 'command' : 'zwei' }
diff --git a/tests/qapi-schema/indented-expr.out b/tests/qapi-schema/indented-expr.out
index 98af89a..b5ce915 100644
--- a/tests/qapi-schema/indented-expr.out
+++ b/tests/qapi-schema/indented-expr.out
@@ -1,3 +1,3 @@
-[OrderedDict([('id', 'eins')]), OrderedDict([('id', 'zwei')])]
+[OrderedDict([('command', 'eins')]), OrderedDict([('command', 'zwei')])]
 []
 []
diff --git a/tests/qapi-schema/missing-type.err b/tests/qapi-schema/missing-type.err
index e69de29..19b7c49 100644
--- a/tests/qapi-schema/missing-type.err
+++ b/tests/qapi-schema/missing-type.err
@@ -0,0 +1 @@
+tests/qapi-schema/missing-type.json:2: expression is missing metatype
diff --git a/tests/qapi-schema/missing-type.exit b/tests/qapi-schema/missing-type.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/missing-type.exit
+++ b/tests/qapi-schema/missing-type.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/missing-type.json b/tests/qapi-schema/missing-type.json
index 1696f5c..ff5349d 100644
--- a/tests/qapi-schema/missing-type.json
+++ b/tests/qapi-schema/missing-type.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an expression with missing metatype
+# we reject an expression with missing metatype
 { 'data': { } }
diff --git a/tests/qapi-schema/missing-type.out b/tests/qapi-schema/missing-type.out
index 67fd4fa..e69de29 100644
--- a/tests/qapi-schema/missing-type.out
+++ b/tests/qapi-schema/missing-type.out
@@ -1,3 +0,0 @@
-[OrderedDict([('data', OrderedDict())])]
-[]
-[]
diff --git a/tests/qapi-schema/unknown-expr-key.err b/tests/qapi-schema/unknown-expr-key.err
index e69de29..3b35508 100644
--- a/tests/qapi-schema/unknown-expr-key.err
+++ b/tests/qapi-schema/unknown-expr-key.err
@@ -0,0 +1 @@
+tests/qapi-schema/unknown-expr-key.json:2: type 'bar' has unknown key 'bogus'
diff --git a/tests/qapi-schema/unknown-expr-key.exit b/tests/qapi-schema/unknown-expr-key.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/unknown-expr-key.exit
+++ b/tests/qapi-schema/unknown-expr-key.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/unknown-expr-key.json b/tests/qapi-schema/unknown-expr-key.json
index 1e9282d..ba7bdf3 100644
--- a/tests/qapi-schema/unknown-expr-key.json
+++ b/tests/qapi-schema/unknown-expr-key.json
@@ -1,2 +1,2 @@
-# FIXME: we should reject an expression with unknown top-level keys
+# we reject an expression with unknown top-level keys
 { 'type': 'bar', 'data': { 'string': 'str'}, 'bogus': { } }
diff --git a/tests/qapi-schema/unknown-expr-key.out b/tests/qapi-schema/unknown-expr-key.out
index c93f020..e69de29 100644
--- a/tests/qapi-schema/unknown-expr-key.out
+++ b/tests/qapi-schema/unknown-expr-key.out
@@ -1,3 +0,0 @@
-[OrderedDict([('type', 'bar'), ('data', OrderedDict([('string', 'str')])), ('bogus', OrderedDict())])]
-[]
-[OrderedDict([('type', 'bar'), ('data', OrderedDict([('string', 'str')])), ('bogus', OrderedDict())])]
