diff --git a/src/main_grammar.cpp b/src/main_grammar.cpp
index 97f99ab..4506e0d 100644
--- a/src/main_grammar.cpp
+++ b/src/main_grammar.cpp
@@ -461,10 +461,14 @@ namespace quickbook
             ;
 
         local.macro =
-            // must not be followed by alpha or underscore
-            cl::eps_p(actions.macro
-                >> (cl::eps_p - (cl::alpha_p | '_')))
-            >> actions.macro                    [actions.do_macro]
+            cl::eps_p
+            (   (   actions.macro
+                >>  ~cl::eps_p(cl::alpha_p | '_')
+                                                // must not be followed by alpha or underscore
+                )
+                &   macro_identifier            // must be a valid macro for the current version
+            )
+            >>  actions.macro                   [actions.do_macro]
             ;
 
         local.template_ =
@@ -585,7 +589,7 @@ namespace quickbook
                 [
                     actions.to_value()
                     [
-                        cl::eps_p(actions.macro >> local.simple_markup_end)
+                        cl::eps_p((actions.macro & macro_identifier) >> local.simple_markup_end)
                     >>  actions.macro       [actions.do_macro]
                     |   ~cl::eps_p(cl::f_ch_p(local.simple_markup.mark))
                     >>  +(  ~cl::eps_p
@@ -717,7 +721,6 @@ namespace quickbook
             '[' >> *(local.line_dummy_block | (cl::anychar_p - (cl::eol_p | ']'))) >> ']'
             ;
 
-        // TODO: Prevent an old macro from being used in a 1.6 file.
         macro_identifier =
                 qbk_since(106u)
             >>  +(cl::anychar_p - (cl::space_p | '[' | '\\' | ']'))
diff --git a/test/versions/Jamfile.v2 b/test/versions/Jamfile.v2
index 0ac3f44..ccb46dc 100644
--- a/test/versions/Jamfile.v2
+++ b/test/versions/Jamfile.v2
@@ -15,4 +15,5 @@ import quickbook-testing : quickbook-test quickbook-error-test ;
 
 test-suite quickbook.test :
     [ quickbook-test versions-1_6 ]
+    [ quickbook-test invalid_macro-1_6 ]
     ;
diff --git a/test/versions/invalid_macro-1_6.gold b/test/versions/invalid_macro-1_6.gold
new file mode 100644
index 0000000..cb62412
--- /dev/null
+++ b/test/versions/invalid_macro-1_6.gold
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE article PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
+<article id="invalid_macro_test" last-revision="DEBUG MODE Date: 2000/12/20 12:00:00 $"
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+  <title>Invalid macro test</title>
+  <para>
+    Import:
+  </para>
+  <itemizedlist>
+    <listitem>
+      <simpara>
+        okay
+      </simpara>
+    </listitem>
+    <listitem>
+      <simpara>
+        __invalid\macro__
+      </simpara>
+    </listitem>
+  </itemizedlist>
+  <para>
+    Include:
+  </para>
+  <itemizedlist>
+    <listitem>
+      <simpara>
+        okay
+      </simpara>
+    </listitem>
+    <listitem>
+      <simpara>
+        bad
+      </simpara>
+    </listitem>
+  </itemizedlist>
+</article>
diff --git a/test/versions/invalid_macro-1_6.quickbook b/test/versions/invalid_macro-1_6.quickbook
new file mode 100644
index 0000000..f579f72
--- /dev/null
+++ b/test/versions/invalid_macro-1_6.quickbook
@@ -0,0 +1,14 @@
+[article Invalid macro test
+[quickbook 1.6]
+]
+
+Import:
+
+[import invalid_macro-inc-1_1.qbk]
+
+* __valid__
+* __invalid\macro__
+
+Include:
+
+[include invalid_macro-inc-1_1.qbk]
diff --git a/test/versions/invalid_macro-inc-1_1.qbk b/test/versions/invalid_macro-inc-1_1.qbk
new file mode 100644
index 0000000..c44bd67
--- /dev/null
+++ b/test/versions/invalid_macro-inc-1_1.qbk
@@ -0,0 +1,7 @@
+[quickbook 1.1]
+
+[def __valid__ okay]
+[def __invalid\macro__ bad]
+
+* __valid__
+* __invalid\macro__