diff --git a/var/spack/repos/builtin/packages/gnuplot/package.py b/var/spack/repos/builtin/packages/gnuplot/package.py
index 59e527fcde47738b6659013ad86a30db7765dabc..0f1689b6cf1f6ee878611899691f79358523984b 100644
--- a/var/spack/repos/builtin/packages/gnuplot/package.py
+++ b/var/spack/repos/builtin/packages/gnuplot/package.py
@@ -63,6 +63,7 @@ class Gnuplot(AutotoolsPackage):
     depends_on('cairo@1.2:', when='+cairo')
     depends_on('wxwidgets', when='+wx')
     depends_on('pango@1.10:', when='+wx')
+    depends_on('libsm', when='+wx')
     depends_on('pango@1.10:', when='+cairo')
     depends_on('libx11', when='+X')
     depends_on('qt@5.7:+opengl', when='+qt')