diff --git a/lib/puppet/util/command_line/trollop.rb b/lib/puppet/util/command_line/trollop.rb
index 8b0fba147aa..0f7a6778d9d 100644
--- a/lib/puppet/util/command_line/trollop.rb
+++ b/lib/puppet/util/command_line/trollop.rb
@@ -335,9 +335,21 @@ def parse cmdline = ARGV
               when /^-([^-])$/
                 @short[::Regexp.last_match(1)]
               when /^--no-([^-]\S*)$/
-                @long["[no-]#{::Regexp.last_match(1)}"]
+                possible_match = @long["[no-]#{::Regexp.last_match(1)}"]
+                if !possible_match
+                  Puppet.warning _("Partial argument match detected: %{arg}. Partial argument matching will be deprecated in Puppet 9.") % { arg: arg }
+                  @long["[no-]#{::Regexp.last_match(1).tr('-', '_')}"] || @long["[no-]#{::Regexp.last_match(1).tr('_', '-')}"]
+                else
+                  possible_match
+                end
               when /^--([^-]\S*)$/
-                @long[::Regexp.last_match(1)] || @long["[no-]#{::Regexp.last_match(1)}"]
+                possible_match = @long[::Regexp.last_match(1)] || @long["[no-]#{::Regexp.last_match(1)}"]
+                if !possible_match
+                  Puppet.warning _("Partial argument match detected: %{arg}. Partial argument matching will be deprecated in Puppet 9.") % { arg: arg }
+                  @long[::Regexp.last_match(1).tr('-', '_')] || @long[::Regexp.last_match(1).tr('_', '-')] || @long["[no-]#{::Regexp.last_match(1).tr('-', '_')}"] || @long["[no-]#{::Regexp.last_match(1).tr('_', '-')}"]
+                else
+                  possible_match
+                end
               else
                 raise CommandlineError, _("invalid argument syntax: '%{arg}'") % { arg: arg }
               end
diff --git a/spec/unit/util/command_line_utils/puppet_option_parser_spec.rb b/spec/unit/util/command_line_utils/puppet_option_parser_spec.rb
index c8365581600..aa64c1dd242 100644
--- a/spec/unit/util/command_line_utils/puppet_option_parser_spec.rb
+++ b/spec/unit/util/command_line_utils/puppet_option_parser_spec.rb
@@ -13,6 +13,24 @@
       )
     end
 
+    it "parses a 'long' option with a value and converts '-' to '_' & warns" do
+      parses(
+        :option => ["--an_gry", "Angry", :REQUIRED],
+        :from_arguments => ["--an-gry", "foo"],
+        :expects => "foo"
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --an-gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
+    it "parses a 'long' option with a value and converts '_' to '-' & warns" do
+      parses(
+        :option => ["--an-gry", "Angry", :REQUIRED],
+        :from_arguments => ["--an_gry", "foo"],
+        :expects => "foo"
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --an_gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
     it "parses a 'short' option with a value" do
       parses(
         :option => ["--angry", "-a", "Angry", :REQUIRED],
@@ -39,6 +57,24 @@
       )
     end
 
+    it "converts '_' to '-' with a 'long' option & warns" do
+      parses(
+        :option => ["--an-gry", "Angry", :NONE],
+        :from_arguments => ["--an_gry"],
+        :expects => true
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --an_gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
+    it "converts '-' to '_' with a 'long' option & warns" do
+      parses(
+        :option => ["--an_gry", "Angry", :NONE],
+        :from_arguments => ["--an-gry"],
+        :expects => true
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --an-gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
     it "parses a 'short' option" do
       parses(
         :option => ["--angry", "-a", "Angry", :NONE],
@@ -55,6 +91,42 @@
       )
     end
 
+    it "resolves '-' to '_' with '--no-blah' syntax" do
+      parses(
+        :option => ["--[no-]an_gry", "Angry", :NONE],
+        :from_arguments => ["--no-an-gry"],
+        :expects => false
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --no-an-gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
+    it "resolves '_' to '-' with '--no-blah' syntax" do
+      parses(
+        :option => ["--[no-]an-gry", "Angry", :NONE],
+        :from_arguments => ["--no-an_gry"],
+        :expects => false
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --no-an_gry. Partial argument matching will be deprecated in Puppet 9./)
+    end
+
+    it "resolves '-' to '_' & warns when option is defined with '--no-blah syntax' but argument is given in '--option' syntax" do
+      parses(
+        :option => ["--[no-]rag-e", "Rage", :NONE],
+        :from_arguments => ["--rag_e"],
+        :expects => true
+      )
+      expect(@logs).to have_matching_log(/Partial argument match detected: --rag_e. Partial argument matching will be deprecated in Puppet 9./)
+  end
+
+  it "resolves '_' to '-' & warns when option is defined with '--no-blah syntax' but argument is given in '--option' syntax" do
+    parses(
+      :option => ["--[no-]rag_e", "Rage", :NONE],
+      :from_arguments => ["--rag-e"],
+      :expects => true
+    )
+    expect(@logs).to have_matching_log(/Partial argument match detected: --rag-e. Partial argument matching will be deprecated in Puppet 9./)
+  end
+
     it "overrides a previous argument with a later one" do
       parses(
         :option => ["--[no-]rage", "Rage", :NONE],