diff --git a/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/BaseExtractorTest.groovy b/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/BaseExtractorTest.groovy
index 696ddc50..84ba64c2 100644
--- a/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/BaseExtractorTest.groovy
+++ b/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/BaseExtractorTest.groovy
@@ -205,7 +205,7 @@ abstract class BaseExtractorTest extends Specification {
     }
 
     @CompileStatic
-    private static class JsonRepositorySnapshotLoader {
+    protected static class JsonRepositorySnapshotLoader {
         private static final String SCHEMA = "schema/github-repository-snapshot-schema.json"
         private final File manifestFile
 
@@ -214,14 +214,14 @@ abstract class BaseExtractorTest extends Specification {
         }
 
         @Memoized
-        protected Object jsonRepositorySnapshot() {
+        protected Map jsonRepositorySnapshot() {
             def jsonSlurper = new JsonSlurper()
             println(manifestFile.text)
             JsonSchema schema = createSchemaValidator()
             ObjectMapper mapper = new ObjectMapper()
             JsonNode node = mapper.readTree(manifestFile)
             validateAgainstJsonSchema(schema, node)
-            return jsonSlurper.parse(manifestFile)
+            return jsonSlurper.parse(manifestFile) as Map
         }
 
         private static void validateAgainstJsonSchema(JsonSchema schema, JsonNode json) {
diff --git a/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/DependencyExtractorConfigTest.groovy b/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/DependencyExtractorConfigTest.groovy
new file mode 100644
index 00000000..b7a5dd4a
--- /dev/null
+++ b/plugin-test/src/test/groovy/org/gradle/github/dependencygraph/DependencyExtractorConfigTest.groovy
@@ -0,0 +1,52 @@
+package org.gradle.github.dependencygraph
+
+import org.gradle.test.fixtures.maven.MavenModule
+
+class DependencyExtractorConfigTest extends BaseExtractorTest {
+    private MavenModule foo
+    private File settingsFile
+    private File buildFile
+
+    def setup() {
+        applyDependencyGraphPlugin()
+        establishEnvironmentVariables()
+
+        foo = mavenRepo.module("org.test", "foo", "1.0").publish()
+
+        settingsFile = file("settings.gradle") << """
+            rootProject.name = 'a'    
+        """
+
+        buildFile = file("build.gradle") << """
+            apply plugin: 'java'
+
+            repositories {
+                maven { url "${mavenRepo.uri}" }
+            }            
+        """
+    }
+
+    def "can override env vars with system properties"() {
+        given:
+        buildFile << """
+        dependencies {
+            implementation "org.test:foo:1.0"
+        }
+        """
+
+        when:
+        executer
+            .withArgument("-Dorg.gradle.github.env.GITHUB_DEPENDENCY_GRAPH_JOB_CORRELATOR=TEST_CORRELATOR")
+            .withArgument("-Dorg.gradle.github.env.GITHUB_REF=refs/my-branch/foo")
+        run()
+
+        then:
+        def manifestFile = reportDir.file("TEST_CORRELATOR.json")
+        def snapshot = new JsonRepositorySnapshotLoader(manifestFile).jsonRepositorySnapshot()
+        assert snapshot.sha == environmentVars.sha
+        assert snapshot.ref == "refs/my-branch/foo"
+        def job = snapshot.job as Map
+        assert job.correlator == "TEST_CORRELATOR"
+        assert job.id == environmentVars.jobId
+    }
+}
diff --git a/plugin/src/main/kotlin/org/gradle/github/dependencygraph/internal/util/EnvironmentVariableLoader.kt b/plugin/src/main/kotlin/org/gradle/github/dependencygraph/internal/util/EnvironmentVariableLoader.kt
index 6cb2177e..407b7362 100644
--- a/plugin/src/main/kotlin/org/gradle/github/dependencygraph/internal/util/EnvironmentVariableLoader.kt
+++ b/plugin/src/main/kotlin/org/gradle/github/dependencygraph/internal/util/EnvironmentVariableLoader.kt
@@ -9,8 +9,8 @@ internal interface EnvironmentVariableLoader {
     interface Default {
         fun Gradle.loadEnvironmentVariable(envName: String, default: String? = null): Provider<String> =
             service<ProviderFactory>().run {
-                environmentVariable(envName)
-                    .orElse(systemProperty(ENV_VIA_SYS_PROP_PREFIX + envName))
+                systemProperty(ENV_VIA_SYS_PROP_PREFIX + envName)
+                    .orElse(environmentVariable(envName))
                     .orElse(provider {
                         default ?: throwEnvironmentVariableMissingException(envName)
                     })
@@ -19,8 +19,8 @@ internal interface EnvironmentVariableLoader {
 
     interface Legacy {
         fun Gradle.loadEnvironmentVariable(envName: String, default: String? = null): String {
-            return System.getenv()[envName]
-                ?: System.getProperty(ENV_VIA_SYS_PROP_PREFIX + envName)
+            return System.getProperty(ENV_VIA_SYS_PROP_PREFIX + envName)
+                ?: System.getenv()[envName]
                 ?: default
                 ?: throwEnvironmentVariableMissingException(envName)
         }