diff --git a/lib/puppet/parser/functions/sha1.rb b/lib/puppet/parser/functions/sha1.rb
index 4906f8a299..1bceafb46b 100644
--- a/lib/puppet/parser/functions/sha1.rb
+++ b/lib/puppet/parser/functions/sha1.rb
@@ -2,6 +2,14 @@
 
 require 'digest/sha1'
 
-Puppet::Parser::Functions.newfunction(:sha1, :type => :rvalue, :arity => 1, :doc => "Returns a SHA1 hash value from a provided string.") do |args|
+Puppet::Parser::Functions.newfunction(:sha1, :type => :rvalue, :arity => 1, :doc => "Returns a SHA1 hash value from a provided string.
+
+  *Deprecated:* this function will be removed in a future release. Use the
+  `sha256()` function from the `puppetlabs-stdlib` module instead.") do |args|
+  Puppet.puppet_deprecation_warning(
+    _("The sha1() function is deprecated and will be removed in a future release. " \
+      "Use the sha256() function from the puppetlabs-stdlib module instead."),
+    key: 'puppet-sha1-function-deprecated'
+  )
   Digest::SHA1.hexdigest(args[0])
 end