diff --git a/var/spack/repos/builtin/packages/r-htmltools/package.py b/var/spack/repos/builtin/packages/r-htmltools/package.py
index 6c8d1e50c8..4a6df7580c 100644
--- a/var/spack/repos/builtin/packages/r-htmltools/package.py
+++ b/var/spack/repos/builtin/packages/r-htmltools/package.py
@@ -7,15 +7,20 @@
 
 
 class RHtmltools(RPackage):
-    """Tools for HTML generation and output."""
+    """Tools for HTML
+
+    Tools for HTML generation and output."""
 
     homepage = "https://github.com/rstudio/htmltools"
     url      = "https://cloud.r-project.org/src/contrib/htmltools_0.3.6.tar.gz"
     list_url = "https://cloud.r-project.org/src/contrib/Archive/htmltools"
 
+    version('0.5.1', sha256='6ac82e4451f9558ceb541ea659a736b2ab3245827832b44d3661e7a4d91f6307')
     version('0.3.6', sha256='44affb82f9c2fd76c9e2b58f9229adb003217932b68c3fdbf1327c8d74c868a2')
     version('0.3.5', sha256='29fb7e075744bbffdff8ba4fce3860076de66f39a59a100ee4cfb4fc00722b49')
 
     depends_on('r@2.14.1:', type=('build', 'run'))
     depends_on('r-digest', type=('build', 'run'))
-    depends_on('r-rcpp', type=('build', 'run'))
+    depends_on('r-base64enc', when='@0.5.1:', type=('build', 'run'))
+    depends_on('r-rlang', when='@0.5.1:', type=('build', 'run'))
+    depends_on('r-rcpp', when=' @:0.3.6', type=('build', 'run'))