diff --git a/lib/util.js b/lib/util.js
index cf4b4d6..88f1731 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -297,8 +297,11 @@ exports.propParse = function( data, options )
         name       = parse_data.name || prop;
         keywords   = parse_data.keywords || {};
 
-        if ( options.assumeAbstract || keywords['abstract'] )
+        if ( options.assumeAbstract || keywords[ 'abstract' ] )
         {
+            // may not be set if assumeAbstract is given
+            keywords[ 'abstract' ] = true;
+
             if ( !( value instanceof Array ) )
             {
                 throw TypeError(
diff --git a/test/test-class-implement.js b/test/test-class-implement.js
index 0ee77ba..feb5d7b 100644
--- a/test/test-class-implement.js
+++ b/test/test-class-implement.js
@@ -31,12 +31,13 @@ var common    = require( './common' ),
 ;
 
 
+// test with and without abstract keyword
 var Type = Interface.extend( {
         'abstract foo': [],
     }),
 
     Type2 = Interface.extend( {
-        'abstract foo2': [],
+        foo2: [],
     }),
 
     Foo       = {},