diff --git a/lib/pact_broker/matrix/repository.rb b/lib/pact_broker/matrix/repository.rb
index fe836eb8b..bdecfc43b 100644
--- a/lib/pact_broker/matrix/repository.rb
+++ b/lib/pact_broker/matrix/repository.rb
@@ -60,7 +60,7 @@ def find_all selectors
       def look_up_versions_for_tags(selectors)
         selectors.collect do | selector |
           if selector[:latest_tag]
-            version = version_repository.find_by_latest_tag(selector[:pacticipant_name], selector[:latest_tag])
+            version = version_repository.find_by_pacticpant_name_and_latest_tag(selector[:pacticipant_name], selector[:latest_tag])
             # validation in resource should ensure we always have a version
             {
               pacticipant_name: selector[:pacticipant_name],
diff --git a/lib/pact_broker/matrix/service.rb b/lib/pact_broker/matrix/service.rb
index 6f03c32fa..dcf0dc339 100644
--- a/lib/pact_broker/matrix/service.rb
+++ b/lib/pact_broker/matrix/service.rb
@@ -23,25 +23,32 @@ def find_compatible_pacticipant_versions criteria
       def validate_selectors selectors
         error_messages = []
 
-        selectors.each do | selector |
-          if selector[:pacticipant_name].nil? && selector[:pacticipant_version_number].nil?
+        selectors.each do | s |
+          if s[:pacticipant_name].nil? && s[:pacticipant_version_number].nil?
             error_messages << "Please specify the pacticipant name and version"
-          elsif selector[:pacticipant_name].nil?
+          elsif s[:pacticipant_name].nil?
             error_messages << "Please specify the pacticipant name"
+          else
+            if s.key?(:pacticipant_version_number) && s.key?(:latest_tag)
+              error_messages << "A version and a latest tag cannot both be specified for #{s[:pacticipant_name]}"
+            end
           end
         end
 
         selectors.collect{ |selector| selector[:pacticipant_name] }.compact.each do | pacticipant_name |
           unless pacticipant_service.find_pacticipant_by_name(pacticipant_name)
-            error_messages << "Pacticipant '#{pacticipant_name}' not found"
+            error_messages << "Pacticipant #{pacticipant_name} not found"
           end
         end
 
         if error_messages.empty?
-          selectors.each do | selector |
-            if selector[:pacticipant_version_number]
-              version = version_service.find_by_pacticipant_name_and_number(pacticipant_name: selector[:pacticipant_name], pacticipant_version_number: selector[:pacticipant_version_number])
-              error_messages << "No pact or verification found for #{selector[:pacticipant_name]} version #{selector[:pacticipant_version_number]}" if version.nil?
+          selectors.each do | s |
+            if s[:pacticipant_version_number]
+              version = version_service.find_by_pacticipant_name_and_number(pacticipant_name: s[:pacticipant_name], pacticipant_version_number: s[:pacticipant_version_number])
+              error_messages << "No pact or verification found for #{s[:pacticipant_name]} version #{s[:pacticipant_version_number]}" if version.nil?
+            elsif s[:latest_tag]
+              version = version_service.find_by_pacticpant_name_and_latest_tag(s[:pacticipant_name], s[:latest_tag])
+              error_messages << "No version of #{s[:pacticipant_name]} found with tag #{s[:latest_tag]}" if version.nil?
             end
           end
         end
diff --git a/lib/pact_broker/versions/repository.rb b/lib/pact_broker/versions/repository.rb
index 10553c324..e4312b4fb 100644
--- a/lib/pact_broker/versions/repository.rb
+++ b/lib/pact_broker/versions/repository.rb
@@ -12,7 +12,7 @@ def find_by_pacticipant_id_and_number pacticipant_id, number
         PactBroker::Domain::Version.where(number: number, pacticipant_id: pacticipant_id).single_record
       end
 
-      def find_by_latest_tag pacticipant_name, tag
+      def find_by_pacticpant_name_and_latest_tag pacticipant_name, tag
         PactBroker::Domain::Version
           .select_all_qualified
           .join(:pacticipants, {id: :pacticipant_id}, {implicit_qualifier: :versions})
diff --git a/lib/pact_broker/versions/service.rb b/lib/pact_broker/versions/service.rb
index c21002925..5bc3d5ad3 100644
--- a/lib/pact_broker/versions/service.rb
+++ b/lib/pact_broker/versions/service.rb
@@ -11,6 +11,10 @@ def self.find_by_pacticipant_name_and_number params
         version_repository.find_by_pacticipant_name_and_number params.fetch(:pacticipant_name), params.fetch(:pacticipant_version_number)
       end
 
+      def self.find_by_pacticpant_name_and_latest_tag(pacticipant_name, tag)
+        version_repository.find_by_pacticpant_name_and_latest_tag(pacticipant_name, tag)
+      end
+
       def self.delete version
         tag_repository.delete_by_version_id version.id
         pact_repository.delete_by_version_id version.id
diff --git a/spec/lib/pact_broker/matrix/service_spec.rb b/spec/lib/pact_broker/matrix/service_spec.rb
index 3b5003e46..b28d675a9 100644
--- a/spec/lib/pact_broker/matrix/service_spec.rb
+++ b/spec/lib/pact_broker/matrix/service_spec.rb
@@ -36,7 +36,7 @@ module Matrix
           let(:selectors) { [{ pacticipant_name: "Foo", pacticipant_version_number: "1" }] }
 
           it "returns error messages" do
-            expect(subject.first).to eq "Pacticipant 'Foo' not found"
+            expect(subject.first).to eq "Pacticipant Foo not found"
           end
         end
 
@@ -70,6 +70,49 @@ module Matrix
             expect(subject.first).to eq "Please specify the pacticipant name and version"
           end
         end
+
+        context "when the latest_tag is used instead of a version" do
+          before do
+            td.create_pacticipant("Foo")
+              .create_version("1")
+              .create_tag("prod")
+              .create_pacticipant("Bar")
+              .create_version("2")
+          end
+
+          let(:selectors) { [{ pacticipant_name: "Foo", latest_tag: "prod" }, { pacticipant_name: "Bar", pacticipant_version_number: "2" }] }
+
+          context "when there is a version for the tag" do
+            it "returns no error messages" do
+              expect(subject).to eq []
+            end
+          end
+
+          context "when there is not a version for the tag" do
+
+            let(:selectors) { [{ pacticipant_name: "Foo", latest_tag: "wiffle" }, { pacticipant_name: "Bar", pacticipant_version_number: "2" }] }
+
+            it "returns an error message" do
+              expect(subject).to eq ["No version of Foo found with tag wiffle"]
+            end
+          end
+        end
+
+        context "when the latest_tag is used as well as a version" do
+          before do
+            td.create_pacticipant("Foo")
+              .create_version("1")
+              .create_tag("prod")
+              .create_pacticipant("Bar")
+              .create_version("2")
+          end
+
+          let(:selectors) { [{ pacticipant_name: "Foo", pacticipant_version_number: "1", latest_tag: "prod" }, { pacticipant_name: "Bar", pacticipant_version_number: "2" }] }
+
+          it "returns an error message" do
+            expect(subject).to eq ["A version and a latest tag cannot both be specified for Foo"]
+          end
+        end
       end
     end
   end
diff --git a/spec/lib/pact_broker/versions/repository_spec.rb b/spec/lib/pact_broker/versions/repository_spec.rb
index 313a95521..5f8053552 100644
--- a/spec/lib/pact_broker/versions/repository_spec.rb
+++ b/spec/lib/pact_broker/versions/repository_spec.rb
@@ -10,7 +10,7 @@ module Versions
       let(:version_number) { "1.2.3" }
 
 
-      describe "#find_by_latest_tag" do
+      describe "#find_by_pacticpant_name_and_latest_tag" do
         before do
           td.create_consumer("Bar")
             .create_consumer_version("2.3.4")
@@ -23,7 +23,7 @@ module Versions
             .create_consumer_version("5.6.7")
         end
 
-        subject { Repository.new.find_by_latest_tag("Foo", "prod") }
+        subject { Repository.new.find_by_pacticpant_name_and_latest_tag("Foo", "prod") }
 
         it "returns the most recent version that has the specified tag" do