diff --git a/lib/spack/docs/packaging_guide.rst b/lib/spack/docs/packaging_guide.rst
index 6bafaecc7d..70def5c39a 100644
--- a/lib/spack/docs/packaging_guide.rst
+++ b/lib/spack/docs/packaging_guide.rst
@@ -1307,9 +1307,9 @@ The dependency types are:
 
 If not specified, ``type`` is assumed to be ``("build", "link")``. This is the
 common case for compiled language usage. Also available are the aliases
-``alldeps`` for all dependency types and ``nolink`` (``("build", "run")``) for
-use by dependencies which are not expressed via a linker (e.g., Python or Lua
-module loading).
+``"alldeps"`` for all dependency types and ``"nolink"`` (``("build", "run")``)
+for use by dependencies which are not expressed via a linker (e.g., Python or
+Lua module loading).
 
 .. _setup-dependent-environment:
 
diff --git a/lib/spack/spack/directives.py b/lib/spack/spack/directives.py
index 88d2aaf472..e92dd6fb67 100644
--- a/lib/spack/spack/directives.py
+++ b/lib/spack/spack/directives.py
@@ -189,7 +189,7 @@ def _depends_on(pkg, spec, when=None, type=None):
         type = ('build', 'link')
 
     if isinstance(type, str):
-        type = (type,)
+        type = spack.spec.special_types.get(type, (type,))
 
     for deptype in type:
         if deptype not in spack.spec.alldeps:
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index e694f2b2da..8bdae0445e 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -155,6 +155,10 @@
 # Special types of dependencies.
 alldeps = ('build', 'link', 'run')
 nolink = ('build', 'run')
+special_types = {
+    'alldeps': alldeps,
+    'nolink': nolink,
+}
 
 
 def index_specs(specs):
@@ -542,7 +546,8 @@ def _deptype_norm(self, deptype):
             return alldeps
         # Force deptype to be a set object so that we can do set intersections.
         if isinstance(deptype, str):
-            return (deptype,)
+            # Support special deptypes.
+            return special_types.get(deptype, (deptype,))
         return deptype
 
     def _find_deps(self, where, deptype):