diff --git a/OpenBMCMapper.py b/OpenBMCMapper.py
index 3e7a745..ef49637 100644
--- a/OpenBMCMapper.py
+++ b/OpenBMCMapper.py
@@ -24,6 +24,10 @@
 MAPPER_PATH = '/org/openbmc/objectmapper/objectmapper'
 ENUMERATE_IFACE = 'org.openbmc.Object.Enumerate'
 
+class MapperNotFoundException(Exception):
+	def __init__(self, msg):
+		super(MapperNotFoundException, self).__init__(msg)
+
 class Path:
 	def __init__(self, path):
 		self.parts = filter(bool, path.split('/'))
diff --git a/phosphor-mapper b/phosphor-mapper
index 5bdcd8d..e9aa6dc 100644
--- a/phosphor-mapper
+++ b/phosphor-mapper
@@ -133,15 +133,24 @@
 
 	@dbus.service.method(OpenBMCMapper.MAPPER_IFACE, 's', 'a{sas}')
 	def GetObject(self, path):
-		return self.cache[path]
+		o = self.cache.get(path)
+		if not o:
+			raise MapperNotFoundException(path)
+		return o
 
 	@dbus.service.method(OpenBMCMapper.MAPPER_IFACE, 'si', 'as')
 	def GetSubTreePaths(self, path, depth):
-		return self.cache.iterkeys(path, depth)
+		try:
+			return self.cache.iterkeys(path, depth)
+		except KeyError:
+			raise MapperNotFoundException(path)
 
 	@dbus.service.method(OpenBMCMapper.MAPPER_IFACE, 'si', 'a{sa{sas}}')
 	def GetSubTree(self, path, depth):
-		return { x:y for x, y in self.cache.dataitems(path, depth) }
+		try:
+			return { x:y for x, y in self.cache.dataitems(path, depth) }
+		except KeyError:
+			raise MapperNotFoundException(path)
 
 class BusWrapper:
 	def __init__(self, bus):