diff --git a/bitbake/lib/bb/build.py b/bitbake/lib/bb/build.py
index a4deb00..5e508fe 100644
--- a/bitbake/lib/bb/build.py
+++ b/bitbake/lib/bb/build.py
@@ -771,21 +771,22 @@ def add_tasks(tasklist, d):
             task_deps['tasks'].append(task)

         flags = d.getVarFlags(task)
-        def getTask(name):
+        def getTask(name,isFlag=False):
             if not name in task_deps:
                 task_deps[name] = {}
             if name in flags:
                 deptask = d.expand(flags[name])
-                task_deps[name][task] = deptask
+                if not isFlag or deptask != "0":
+                    task_deps[name][task] = deptask
         getTask('depends')
         getTask('rdepends')
         getTask('deptask')
         getTask('rdeptask')
         getTask('recrdeptask')
         getTask('recideptask')
-        getTask('nostamp')
-        getTask('fakeroot')
-        getTask('noexec')
+        getTask('nostamp',True)
+        getTask('fakeroot',True)
+        getTask('noexec',True)
         getTask('umask')
         task_deps['parents'][task] = []
         if 'deps' in flags:
diff --git a/bitbake/lib/bb/parse/ast.py b/bitbake/lib/bb/parse/ast.py
index 8b9baa7..bf06f62 100644
--- a/bitbake/lib/bb/parse/ast.py
+++ b/bitbake/lib/bb/parse/ast.py
@@ -69,6 +69,23 @@ class ExportNode(AstNode):
     def eval(self, data):
         data.setVarFlag(self.var, "export", 1, op = 'exported')

+class UnsetNode(AstNode):
+    def __init__(self, filename, lineno, var):
+        AstNode.__init__(self, filename, lineno)
+        self.var = var
+
+    def eval(self, data):
+        data.delVar(self.var)
+
+class UnsetFlagNode(AstNode):
+    def __init__(self, filename, lineno, var, flag):
+        AstNode.__init__(self, filename, lineno)
+        self.var = var
+        self.flag = flag
+
+    def eval(self, data):
+        data.delVarFlag(self.var, self.flag)
+
 class DataNode(AstNode):
     """
     Various data related updates. For the sake of sanity
@@ -270,6 +287,12 @@ def handleInclude(statements, filename, lineno, m, force):
 def handleExport(statements, filename, lineno, m):
     statements.append(ExportNode(filename, lineno, m.group(1)))

+def handleUnset(statements, filename, lineno, m):
+    statements.append(UnsetNode(filename, lineno, m.group(1)))
+
+def handleUnsetFlag(statements, filename, lineno, m):
+    statements.append(UnsetFlagNode(filename, lineno, m.group(1), m.group(2)))
+
 def handleData(statements, filename, lineno, groupd):
     statements.append(DataNode(filename, lineno, groupd))

diff --git a/bitbake/lib/bb/parse/parse_py/ConfHandler.py b/bitbake/lib/bb/parse/parse_py/ConfHandler.py
index b971292..875250d 100644
--- a/bitbake/lib/bb/parse/parse_py/ConfHandler.py
+++ b/bitbake/lib/bb/parse/parse_py/ConfHandler.py
@@ -57,6 +57,8 @@ __config_regexp__  = re.compile( r"""
 __include_regexp__ = re.compile( r"include\s+(.+)" )
 __require_regexp__ = re.compile( r"require\s+(.+)" )
 __export_regexp__ = re.compile( r"export\s+([a-zA-Z0-9\-_+.${}/]+)$" )
+__unset_regexp__ = re.compile( r"unset\s+([a-zA-Z0-9\-_+.${}/]+)$" )
+__unset_flag_regexp__ = re.compile( r"unset\s+([a-zA-Z0-9\-_+.${}/]+)\[([a-zA-Z0-9\-_+.${}/]+)\]$" )

 def init(data):
     topdir = data.getVar('TOPDIR', False)
@@ -185,6 +187,16 @@ def feeder(lineno, s, fn, statements):
         ast.handleExport(statements, fn, lineno, m)
         return

+    m = __unset_regexp__.match(s)
+    if m:
+        ast.handleUnset(statements, fn, lineno, m)
+        return
+
+    m = __unset_flag_regexp__.match(s)
+    if m:
+        ast.handleUnsetFlag(statements, fn, lineno, m)
+        return
+
     raise ParseError("unparsed line: '%s'" % s, fn, lineno);

 # Add us to the handlers list