diff --git a/sentry-android-core/src/test/java/io/sentry/android/core/InternalSentrySdkTest.kt b/sentry-android-core/src/test/java/io/sentry/android/core/InternalSentrySdkTest.kt
index ba0322c7a1..031df4c523 100644
--- a/sentry-android-core/src/test/java/io/sentry/android/core/InternalSentrySdkTest.kt
+++ b/sentry-android-core/src/test/java/io/sentry/android/core/InternalSentrySdkTest.kt
@@ -38,13 +38,13 @@ import java.io.ByteArrayOutputStream
 import java.io.InputStreamReader
 import java.util.concurrent.atomic.AtomicReference
 import kotlin.test.BeforeTest
-import kotlin.test.Ignore
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertNotEquals
 import kotlin.test.assertNotNull
 import kotlin.test.assertNull
 import kotlin.test.assertTrue
+import org.awaitility.kotlin.await
 import org.junit.runner.RunWith
 import org.mockito.kotlin.mock
 import org.mockito.kotlin.whenever
@@ -87,6 +87,12 @@ class InternalSentrySdkTest {
         }
       }
 
+      // Sentry.init moves any leftover session.json to previous_session.json on the executor. Wait
+      // for that to finish, otherwise it can move the session a test has just persisted. Test
+      // options set sessionFlushTimeoutMillis to 0, so waitPreviousSessionFlush() only polls.
+      val cache = options.envelopeDiskCache as EnvelopeCache
+      await.until { cache.waitPreviousSessionFlush() }
+
       capturedEnvelopes.clear()
     }
 
@@ -634,14 +640,6 @@ class InternalSentrySdkTest {
     assertThat(activeSession.get().sessionId).isNotEqualTo(oldSid)
   }
 
-  // Flaky: intermittently fails with FileNotFoundException reading session.json at the
-  // `sessionFile.reader()` call below, i.e. persistCurrentSession() did not leave a session file
-  // on disk by the time this test reads it back. Seen across unrelated PRs, e.g.:
-  // https://scans.gradle.com/s/55fnn6xhtfyfq/tests/task/:sentry-android-core:testReleaseUnitTest/details/io.sentry.android.core.InternalSentrySdkTest/updateSessionForDroppedEventNonTerminating%20flags%20an%20unhandled%20error%20without%20sending%20an%20envelope?top-execution=1
-  // https://scans.gradle.com/s/ojzzz4yxag7rw/tests/task/:sentry-android-core:testReleaseUnitTest/details/io.sentry.android.core.InternalSentrySdkTest/updateSessionForDroppedEventNonTerminating%20flags%20an%20unhandled%20error%20without%20sending%20an%20envelope?top-execution=1
-  // Disabling until root-caused; see https://github.com/getsentry/sentry-java/pull/5990 for the
-  // code under test.
-  @Ignore("Flaky: intermittently fails to find the persisted session.json, needs root-causing")
   @Test
   fun `updateSessionForDroppedEventNonTerminating flags an unhandled error without sending an envelope`() {
     val fixture = Fixture()