diff --git a/var/spack/repos/builtin/packages/pythia8/package.py b/var/spack/repos/builtin/packages/pythia8/package.py
index 9b9ea46c43a..eeda2b680d7 100644
--- a/var/spack/repos/builtin/packages/pythia8/package.py
+++ b/var/spack/repos/builtin/packages/pythia8/package.py
@@ -97,8 +97,12 @@ def configure_args(self):
             args += '--without-mg5mes'
 
         args += self.with_or_without('hepmc3', activation_value='prefix')
-        args += self.with_or_without('fastjet3', activation_value='prefix',
-                                     variant='fastjet')
+
+        if '+fastjet' in self.spec:
+            args += '--with-fastjet3=' + self.spec['fastjet'].prefix
+        else:
+            args += '--without-fastjet3'
+
         args += self.with_or_without('evtgen', activation_value='prefix')
         args += self.with_or_without('root', activation_value='prefix')
         args += self.with_or_without('rivet', activation_value='prefix')