diff --git a/var/spack/repos/builtin/packages/isaac-server/package.py b/var/spack/repos/builtin/packages/isaac-server/package.py
index b9954b0a172..8e345b1ea2e 100644
--- a/var/spack/repos/builtin/packages/isaac-server/package.py
+++ b/var/spack/repos/builtin/packages/isaac-server/package.py
@@ -31,7 +31,9 @@ class IsaacServer(CMakePackage):
     homepage = "http://computationalradiationphysics.github.io/isaac/"
     url      = "https://github.com/ComputationalRadiationPhysics/isaac/archive/v1.3.0.tar.gz"
 
-    root_cmakelists_dir = 'server'
+    @property
+    def root_cmakelists_dir(self):
+        return join_path(self.stage.source_path, 'server')
 
     version('develop', branch='dev',
             git='https://github.com/ComputationalRadiationPhysics/isaac.git')
diff --git a/var/spack/repos/builtin/packages/isaac/package.py b/var/spack/repos/builtin/packages/isaac/package.py
index fd3b9799850..390006174e8 100644
--- a/var/spack/repos/builtin/packages/isaac/package.py
+++ b/var/spack/repos/builtin/packages/isaac/package.py
@@ -31,7 +31,9 @@ class Isaac(CMakePackage):
     homepage = "http://computationalradiationphysics.github.io/isaac/"
     url      = "https://github.com/ComputationalRadiationPhysics/isaac/archive/v1.3.0.tar.gz"
 
-    root_cmakelists_dir = 'lib'
+    @property
+    def root_cmakelists_dir(self):
+        return join_path(self.stage.source_path, 'lib')
 
     version('develop', branch='dev',
             git='https://github.com/ComputationalRadiationPhysics/isaac.git')