diff --git a/src/main/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactory.groovy b/src/main/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactory.groovy
index 171e04c..f28dae2 100644
--- a/src/main/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactory.groovy
+++ b/src/main/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactory.groovy
@@ -24,11 +24,19 @@ class ServiceInfoFactory {
                                 'travis_pull_request': env.get('TRAVIS_PULL_REQUEST')]
                 )
             } else if (envIsCircleci(env)) {
+                String prId = env.get('CI_PULL_REQUEST')
+                if (prId != null) {
+                   // CircleCI CI_PULL_REQUEST is the full URL, so extract just the PR number
+                   int lastSlashIdx = prId.lastIndexOf('/')
+                   if (lastSlashIdx > -1 && lastSlashIdx + 1 < prId.length()) {
+                       prId = prId.substring(lastSlashIdx + 1)
+                   }
+                }
                 return new ServiceInfo(
                         serviceName: 'circleci',
                         serviceNumber: env.get('CIRCLE_BUILD_NUM'),
                         repoToken: env.get('COVERALLS_REPO_TOKEN'),
-                        servicePullRequest: env.get('CI_PULL_REQUEST'),
+                        servicePullRequest: prId,
                         environment: [
                                 'circleci_build_num': env.get('CIRCLE_BUILD_NUM'),
                                 'branch'            : env.get('CIRCLE_BRANCH'),
diff --git a/src/test/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactoryTest.groovy b/src/test/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactoryTest.groovy
index 36c4fa6..a175217 100644
--- a/src/test/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactoryTest.groovy
+++ b/src/test/groovy/org/kt3k/gradle/plugin/coveralls/domain/ServiceInfoFactoryTest.groovy
@@ -72,14 +72,14 @@ class ServiceInfoFactoryTest {
                 CIRCLECI: 'true',
                 CIRCLE_BUILD_NUM: '12345678',
                 COVERALLS_REPO_TOKEN: 'ABCDEF',
-                CI_PULL_REQUEST: 'pullrequest111',
+                CI_PULL_REQUEST: 'https://github.com/kt3k/coveralls-gradle-plugin/pull/51',
                 CIRCLE_BRANCH: 'branchX',
                 CIRCLE_SHA1: '231asdfadsf424')
 
         assertEquals 'circleci', serviceInfo.serviceName
         assertEquals '12345678', serviceInfo.serviceNumber
         assertEquals 'ABCDEF', serviceInfo.repoToken
-        assertEquals 'pullrequest111', serviceInfo.servicePullRequest
+        assertEquals '51', serviceInfo.servicePullRequest
         assertEquals 'branchX', serviceInfo.environment['branch']
         assertEquals '231asdfadsf424', serviceInfo.environment['commit_sha']
         assertEquals '12345678', serviceInfo.environment['circleci_build_num']