diff --git a/README.md b/README.md
index c26fc26..6a2474c 100644
--- a/README.md
+++ b/README.md
@@ -73,6 +73,8 @@ concourse version 1.2.x and higher and the [`version: every`](http://concourse.c
   See the [`git-config(1)` manual page](https://www.kernel.org/pub/software/scm/git/docs/git-config.html)
   for more information and documentation of existing git options.
 
+* `disallow_forks`: *Optional*. If set to `true` it will only detect pull requests raised from within the same repository. Pull requests from forks will not generate new versions of the resource within Concourse. The default value is `false`.
+
 ## Behavior
 
 ### `check`: Check for new pull requests
diff --git a/assets/check b/assets/check
index d10b27f..16db3a7 100755
--- a/assets/check
+++ b/assets/check
@@ -5,6 +5,8 @@ set -e
 exec 3>&1 # make stdout available as fd 3 for the result
 exec 1>&2 # redirect all output to stderr for logging
 
+. $(dirname $0)/common.sh
+
 payload=$(mktemp $TMPDIR/pullrequest-resource.XXXXXX)
 cat > $payload <&0
 
diff --git a/assets/lib/commands/check.rb b/assets/lib/commands/check.rb
index 166ce57..bc186ef 100755
--- a/assets/lib/commands/check.rb
+++ b/assets/lib/commands/check.rb
@@ -10,7 +10,7 @@ class Check < Commands::Base
 
     def output
       if return_all_versions?
-        repo.pull_requests
+        all_pull_requests
       else
         next_pull_request
       end
@@ -22,11 +22,20 @@ def return_all_versions?
       input['source']['every'] == true
     end
 
+    def disallow_forks?
+      input['source']['disallow_forks'] == true
+    end
+
+    def all_pull_requests
+      repo.pull_requests(disallow_forks: disallow_forks?)
+    end
+
     def next_pull_request
       pull_request = repo.next_pull_request(
         id: input['version']['pr'],
         sha: input['version']['ref'],
-        base: input['source']['base']
+        base: input['source']['base'],
+        disallow_forks: disallow_forks?,
       )
 
       if pull_request
diff --git a/assets/lib/pull_request.rb b/assets/lib/pull_request.rb
index 2a4645d..de0f6c4 100644
--- a/assets/lib/pull_request.rb
+++ b/assets/lib/pull_request.rb
@@ -10,6 +10,10 @@ def ready?
     statuses.empty?
   end
 
+  def from_fork?
+    base_repo != head_repo
+  end
+
   def equals?(id:, sha:)
     [self.sha, self.id.to_s] == [sha, id.to_s]
   end
@@ -36,6 +40,14 @@ def url
 
   private
 
+  def base_repo
+    @pr['base']['repo']['full_name']
+  end
+
+  def head_repo
+    @pr['head']['repo']['full_name']
+  end
+
   def statuses
     @statuses ||= Octokit.statuses(@repo.name, sha).select do |status|
       status['context'] =~ /^concourse-ci/
diff --git a/assets/lib/repository.rb b/assets/lib/repository.rb
index 0b37503..11d8946 100644
--- a/assets/lib/repository.rb
+++ b/assets/lib/repository.rb
@@ -8,10 +8,8 @@ def initialize(name:)
     @name = name
   end
 
-  def pull_requests(args = {})
-    @pull_requests ||= Octokit.pulls(name, pulls_options(args)).map do |pr|
-      PullRequest.new(repo: self, pr: pr)
-    end
+  def pull_requests(base: nil, disallow_forks: false)
+    @pull_requests ||= load_pull_requests(base: base, disallow_forks: disallow_forks)
   end
 
   def pull_request(id:)
@@ -19,21 +17,31 @@ def pull_request(id:)
     PullRequest.new(repo: self, pr: pr)
   end
 
-  def next_pull_request(id: nil, sha: nil, base: nil)
-    return if pull_requests(base: base).empty?
+  def next_pull_request(id: nil, sha: nil, base: nil, disallow_forks: false)
+    return if pull_requests(base: base, disallow_forks: disallow_forks).empty?
 
     if id && sha
-      current = pull_requests.find { |pr| pr.equals?(id: id, sha: sha) }
+      current = pull_requests(disallow_forks: disallow_forks).find { |pr| pr.equals?(id: id, sha: sha) }
       return if current && current.ready?
     end
 
-    pull_requests.find do |pr|
+    pull_requests(disallow_forks: disallow_forks).find do |pr|
       pr != current && pr.ready?
     end
   end
 
   private
 
+  def load_pull_requests(base: nil, disallow_forks: false)
+    pulls = Octokit.pulls(name, pulls_options(base: base)).map do |pr|
+      PullRequest.new(repo: self, pr: pr)
+    end
+    if disallow_forks
+      pulls = pulls.select { |pr| !pr.from_fork? }
+    end
+    pulls
+  end
+
   def pulls_options(base: nil)
     base ? default_opts.merge(base: base) : default_opts
   end
diff --git a/spec/commands/check_spec.rb b/spec/commands/check_spec.rb
index 1aa9b23..7d4afec 100644
--- a/spec/commands/check_spec.rb
+++ b/spec/commands/check_spec.rb
@@ -69,8 +69,9 @@ def stub_json(uri, body)
         stub_json(
           'https://api.github.com:443/repos/jtarchie/test/pulls?direction=asc&per_page=100&sort=updated&state=open',
           [
-            { number: 1, head: { sha: 'abcdef' } },
-            { number: 2, head: { sha: 'zyxwvu' } }
+            { number: 1, head: { sha: 'abcdef', repo: { full_name: 'jtarchie/test' } }, base: { repo: { full_name: 'jtarchie/test' } } },
+            { number: 3, head: { sha: 'ghijkl', repo: { full_name: 'jtarchie/test' } }, base: { repo: { full_name: 'jtarchie/test' } } },
+            { number: 2, head: { sha: 'zyxwvu', repo: { full_name: 'someother/repo' } }, base: { repo: { full_name: 'jtarchie/test' } } },
           ]
         )
       end
@@ -78,7 +79,15 @@ def stub_json(uri, body)
       it 'returns all PRs oldest to newest last' do
         expect(check('source' => { 'repo' => 'jtarchie/test', 'every' => true }, 'version' => {})).to eq [
           { 'ref' => 'abcdef', 'pr' => '1' },
-          { 'ref' => 'zyxwvu', 'pr' => '2' }
+          { 'ref' => 'ghijkl', 'pr' => '3' },
+          { 'ref' => 'zyxwvu', 'pr' => '2' },
+        ]
+      end
+
+      it 'filters out PRs from forked repos when requested' do
+        expect(check('source' => { 'repo' => 'jtarchie/test', 'every' => true, 'disallow_forks' => true }, 'version' => {})).to eq [
+          { 'ref' => 'abcdef', 'pr' => '1' },
+          { 'ref' => 'ghijkl', 'pr' => '3' },
         ]
       end
     end
@@ -158,9 +167,11 @@ def stub_json(uri, body)
 
     context 'when there is more than one open pull request' do
       before do
+        stub_json('https://api.github.com/repos/jtarchie/test/statuses/abcdef', [])
+        stub_json('https://api.github.com/repos/jtarchie/test/statuses/zyxwvu', [])
         stub_json('https://api.github.com/repos/jtarchie/test/pulls?direction=asc&per_page=100&sort=updated&state=open', [
-                    { number: 2, head: { sha: 'zyxwvu' } },
-                    { number: 1, head: { sha: 'abcdef' } }
+                    { number: 2, head: { sha: 'zyxwvu', repo: { full_name: 'someotherowner/repo' } }, base: { repo: { full_name: 'jtarchie/test' } } },
+                    { number: 1, head: { sha: 'abcdef', repo: { full_name: 'jtarchie/test' } }, base: { repo: { full_name: 'jtarchie/test' } } },
                   ])
       end
 
@@ -185,6 +196,18 @@ def stub_json(uri, body)
           expect(check(payload)).to eq []
         end
       end
+
+      context 'and `disallow_forks` is not set' do
+        it 'returns the most recently updated pull request' do
+          expect(check('source' => { 'repo' => 'jtarchie/test' })).to eq [{ 'ref' => 'zyxwvu', 'pr' => '2' }]
+        end
+      end
+
+      context 'and `disallow_forks` is set to true' do
+        it 'returns the most recently updated internal pull request' do
+          expect(check('source' => { 'repo' => 'jtarchie/test', 'disallow_forks' => true })).to eq [{ 'ref' => 'abcdef', 'pr' => '1' }]
+        end
+      end
     end
   end
 end