diff --git a/var/spack/repos/builtin/packages/slepc/package.py b/var/spack/repos/builtin/packages/slepc/package.py
index cd122a58409..65e6607bbca 100644
--- a/var/spack/repos/builtin/packages/slepc/package.py
+++ b/var/spack/repos/builtin/packages/slepc/package.py
@@ -96,7 +96,7 @@ def install(self, spec, prefix):
 
         if '+arpack' in spec:
             options.extend([
-                '--with-arpack-dir=%s' % spec['arpack-ng'].prefix.lib,
+                '--with-arpack-dir=%s' % spec['arpack-ng'].prefix,
             ])
             if spec.satisfies('@:3.12.99'):
                 arpackopt = '--with-arpack-flags'