diff --git a/lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/LDClient.java b/lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/LDClient.java
index 18f314ca..593673ff 100644
--- a/lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/LDClient.java
+++ b/lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/LDClient.java
@@ -31,6 +31,7 @@
 import java.io.UnsupportedEncodingException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -72,6 +73,10 @@ public final class LDClient implements LDClientInterface {
 
   private static final int EXCESSIVE_INIT_WAIT_MILLIS = 60000;
 
+  // The largest start wait the SDK can represent in milliseconds. A longer wait is clamped to it rather than
+  // converted, because converting it would overflow and throw (and would do so after the data system starts).
+  private static final Duration MAX_MILLIS_START_WAIT = Duration.ofMillis(Long.MAX_VALUE);
+
   /**
    * Creates a new client instance that connects to LaunchDarkly with the default configuration.
    * <p>
@@ -259,15 +264,21 @@ public LDClient(String sdkKey, LDConfig config) {
     // Start the data system
     Future<Void> startFuture = dataSystem.start();
     if (!config.startWait.isZero() && !config.startWait.isNegative()) {
+      // Convert the start wait to milliseconds, clamping a wait too large to represent to the maximum rather
+      // than converting it, which would overflow and throw. Only the positive boundary matters here, since
+      // zero and negative waits are excluded above.
+      long startWaitMillis = config.startWait.compareTo(MAX_MILLIS_START_WAIT) >= 0
+          ? Long.MAX_VALUE
+          : config.startWait.toMillis();
       if (!dataSystem.isInitialized()) {
         baseLogger.info("Waiting up to {} milliseconds for LaunchDarkly client to start...",
-            config.startWait.toMillis());
-        if (config.startWait.toMillis() > EXCESSIVE_INIT_WAIT_MILLIS) {
-          baseLogger.warn("LaunchDarkly client created with start wait time of {} milliseconds.  We recommend a timeout of less than {} milliseconds.", config.startWait.toMillis(), EXCESSIVE_INIT_WAIT_MILLIS);
+            startWaitMillis);
+        if (startWaitMillis > EXCESSIVE_INIT_WAIT_MILLIS) {
+          baseLogger.warn("LaunchDarkly client created with start wait time of {} milliseconds.  We recommend a timeout of less than {} milliseconds.", startWaitMillis, EXCESSIVE_INIT_WAIT_MILLIS);
         }
       }
       try {
-        startFuture.get(config.startWait.toMillis(), TimeUnit.MILLISECONDS);
+        startFuture.get(startWaitMillis, TimeUnit.MILLISECONDS);
       } catch (TimeoutException e) {
         baseLogger.error("Timeout encountered waiting for LaunchDarkly client initialization");
       } catch (Exception e) {
diff --git a/lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/LDClientTest.java b/lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/LDClientTest.java
index e313aa68..a53c80f2 100644
--- a/lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/LDClientTest.java
+++ b/lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/LDClientTest.java
@@ -331,6 +331,25 @@ public void willWaitForDataSourceIfWaitMillisIsGreaterThanZero() throws Exceptio
     mocks.verifyAll();
   }
 
+  @Test
+  public void startWaitTooLargeForMillisIsClampedRatherThanOverflowing() throws Exception {
+    // A start wait time too large to represent in milliseconds must be clamped, not converted directly:
+    // converting it throws ArithmeticException, and it would do so after the data source has started, leaving
+    // the data source running with no reference available to close it.
+    LDConfig.Builder config = new LDConfig.Builder()
+        .startWait(Duration.ofSeconds(Long.MAX_VALUE));
+
+    expect(dataSource.start()).andReturn(initFuture);
+    expect(initFuture.get(Long.MAX_VALUE, TimeUnit.MILLISECONDS)).andReturn(null);
+    expect(dataSource.isInitialized()).andReturn(false).anyTimes();
+    mocks.replayAll();
+
+    client = createMockClient(config);
+    assertFalse(client.isInitialized());
+
+    mocks.verifyAll();
+  }
+
   @Test
   public void noWaitForDataSourceIfWaitMillisIsNegative() throws Exception {
     LDConfig.Builder config = new LDConfig.Builder()