diff --git a/var/spack/repos/builtin/packages/plplot/package.py b/var/spack/repos/builtin/packages/plplot/package.py
index d0806069651..7a3bdd8240d 100644
--- a/var/spack/repos/builtin/packages/plplot/package.py
+++ b/var/spack/repos/builtin/packages/plplot/package.py
@@ -38,6 +38,7 @@ class Plplot(CMakePackage):
     depends_on('qt', when='+qt')
     depends_on('tcl', when='+tcl')
     depends_on('wxwidgets', when='+wx')
+    depends_on('libsm', type='link')
 
     depends_on('freetype')
     depends_on('gtkplus')