diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index c4264a819b..4d8c2fcf02 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -112,7 +112,9 @@ and field names within a type, should be all lower case with words
 separated by a hyphen.  However, some existing older commands and
 complex types use underscore; when extending such expressions,
 consistency is preferred over blindly avoiding underscore.  Event
-names should be ALL_CAPS with words separated by underscore.
+names should be ALL_CAPS with words separated by underscore.  Field
+names cannot start with 'has-' or 'has_', as this is reserved for
+tracking optional fields.
 
 Any name (command, event, type, field, or enum value) beginning with
 "x-" is marked experimental, and may be withdrawn or changed
@@ -123,9 +125,10 @@ vendor), even if the rest of the name uses dash (example:
 __com.redhat_drive-mirror).  Other than downstream extensions (with
 leading underscore and the use of dots), all names should begin with a
 letter, and contain only ASCII letters, digits, dash, and underscore.
-It is okay to reuse names that match C keywords; the generator will
-rename a field named "default" in the QAPI to "q_default" in the
-generated C code.
+Names beginning with 'q_' are reserved for the generator: QMP names
+that resemble C keywords or other problematic strings will be munged
+in C to use this prefix.  For example, a field named "default" in
+qapi becomes "q_default" in the generated C code.
 
 In the rest of this document, usage lines are given for each
 expression type, with literal strings written in lower case and
diff --git a/scripts/qapi.py b/scripts/qapi.py
index d53b5c4b45..3ff7b11e61 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -376,7 +376,9 @@ def check_name(expr_info, source, name, allow_optional=False,
     # code always prefixes it with the enum name
     if enum_member:
         membername = '_' + membername
-    if not valid_name.match(membername):
+    # Reserve the entire 'q_' namespace for c_name()
+    if not valid_name.match(membername) or \
+       c_name(membername, False).startswith('q_'):
         raise QAPIExprError(expr_info,
                             "%s uses invalid name '%s'" % (source, name))
 
@@ -488,6 +490,10 @@ def check_type(expr_info, source, value, allow_array=False,
     for (key, arg) in value.items():
         check_name(expr_info, "Member of %s" % source, key,
                    allow_optional=allow_optional)
+        if c_name(key, False).startswith('has_'):
+            raise QAPIExprError(expr_info,
+                                "Member of %s uses reserved name '%s'"
+                                % (source, key))
         # Todo: allow dictionaries to represent default values of
         # an optional argument.
         check_type(expr_info, "Member '%s' of %s" % (key, source), arg,
diff --git a/tests/qapi-schema/reserved-command-q.err b/tests/qapi-schema/reserved-command-q.err
index e69de29bb2..f939e044eb 100644
--- a/tests/qapi-schema/reserved-command-q.err
+++ b/tests/qapi-schema/reserved-command-q.err
@@ -0,0 +1 @@
+tests/qapi-schema/reserved-command-q.json:5: 'command' uses invalid name 'q-unix'
diff --git a/tests/qapi-schema/reserved-command-q.exit b/tests/qapi-schema/reserved-command-q.exit
index 573541ac97..d00491fd7e 100644
--- a/tests/qapi-schema/reserved-command-q.exit
+++ b/tests/qapi-schema/reserved-command-q.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/reserved-command-q.json b/tests/qapi-schema/reserved-command-q.json
index be9944c68a..99f8aae314 100644
--- a/tests/qapi-schema/reserved-command-q.json
+++ b/tests/qapi-schema/reserved-command-q.json
@@ -1,7 +1,5 @@
 # C entity name collision
-# FIXME - This parses, but fails to compile, because it attempts to declare
-# two 'qmp_q_unix' functions (one for 'q-unix', the other because c_name()
-# munges 'unix' to 'q_unix' to avoid reserved word collisions). We should
-# reject attempts to explicitly use 'q_' names, to reserve it for qapi.
+# We reject names like 'q-unix', because they can collide with the mangled
+# name for 'unix' in generated C.
 { 'command': 'unix' }
 { 'command': 'q-unix' }
diff --git a/tests/qapi-schema/reserved-command-q.out b/tests/qapi-schema/reserved-command-q.out
index b31b38ff0d..e69de29bb2 100644
--- a/tests/qapi-schema/reserved-command-q.out
+++ b/tests/qapi-schema/reserved-command-q.out
@@ -1,5 +0,0 @@
-object :empty
-command q-unix None -> None
-   gen=True success_response=True
-command unix None -> None
-   gen=True success_response=True
diff --git a/tests/qapi-schema/reserved-member-has.err b/tests/qapi-schema/reserved-member-has.err
index e69de29bb2..e755771446 100644
--- a/tests/qapi-schema/reserved-member-has.err
+++ b/tests/qapi-schema/reserved-member-has.err
@@ -0,0 +1 @@
+tests/qapi-schema/reserved-member-has.json:5: Member of 'data' for command 'oops' uses reserved name 'has-a'
diff --git a/tests/qapi-schema/reserved-member-has.exit b/tests/qapi-schema/reserved-member-has.exit
index 573541ac97..d00491fd7e 100644
--- a/tests/qapi-schema/reserved-member-has.exit
+++ b/tests/qapi-schema/reserved-member-has.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/reserved-member-has.json b/tests/qapi-schema/reserved-member-has.json
index a2197de6b5..45b9109bdc 100644
--- a/tests/qapi-schema/reserved-member-has.json
+++ b/tests/qapi-schema/reserved-member-has.json
@@ -1,6 +1,5 @@
 # C member name collision
-# FIXME - This parses, but fails to compile, because the C struct is given
-# two 'has_a' members, one from the flag for optional 'a', and the other
-# from member 'has-a'.  Either reject this at parse time, or munge the C
-# names to avoid the collision.
+# We reject names like 'has-a', because they can collide with the flag
+# for an optional 'a' in generated C.
+# TODO we could munge the optional flag name to avoid the collision.
 { 'command': 'oops', 'data': { '*a': 'str', 'has-a': 'str' } }
diff --git a/tests/qapi-schema/reserved-member-has.out b/tests/qapi-schema/reserved-member-has.out
index 5a18b6be8c..e69de29bb2 100644
--- a/tests/qapi-schema/reserved-member-has.out
+++ b/tests/qapi-schema/reserved-member-has.out
@@ -1,6 +0,0 @@
-object :empty
-object :obj-oops-arg
-    member a: str optional=True
-    member has-a: str optional=False
-command oops :obj-oops-arg -> None
-   gen=True success_response=True
diff --git a/tests/qapi-schema/reserved-member-q.err b/tests/qapi-schema/reserved-member-q.err
index e69de29bb2..f3d5dd7818 100644
--- a/tests/qapi-schema/reserved-member-q.err
+++ b/tests/qapi-schema/reserved-member-q.err
@@ -0,0 +1 @@
+tests/qapi-schema/reserved-member-q.json:4: Member of 'data' for struct 'Foo' uses invalid name 'q-unix'
diff --git a/tests/qapi-schema/reserved-member-q.exit b/tests/qapi-schema/reserved-member-q.exit
index 573541ac97..d00491fd7e 100644
--- a/tests/qapi-schema/reserved-member-q.exit
+++ b/tests/qapi-schema/reserved-member-q.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/reserved-member-q.json b/tests/qapi-schema/reserved-member-q.json
index 1602ed3281..62fed8fddf 100644
--- a/tests/qapi-schema/reserved-member-q.json
+++ b/tests/qapi-schema/reserved-member-q.json
@@ -1,6 +1,4 @@
 # C member name collision
-# FIXME - This parses, but fails to compile, because it attempts to declare
-# two 'q_unix' members (one for 'q-unix', the other because c_name()
-# munges 'unix' to 'q_unix' to avoid reserved word collisions). We should
-# reject attempts to explicitly use 'q_' names, to reserve it for qapi.
+# We reject names like 'q-unix', because they can collide with the mangled
+# name for 'unix' in generated C.
 { 'struct': 'Foo', 'data': { 'unix':'int', 'q-unix':'bool' } }
diff --git a/tests/qapi-schema/reserved-member-q.out b/tests/qapi-schema/reserved-member-q.out
index 0d8685aeb0..e69de29bb2 100644
--- a/tests/qapi-schema/reserved-member-q.out
+++ b/tests/qapi-schema/reserved-member-q.out
@@ -1,4 +0,0 @@
-object :empty
-object Foo
-    member unix: int optional=False
-    member q-unix: bool optional=False