diff --git a/xds/src/main/java/io/grpc/xds/ClientXdsClient.java b/xds/src/main/java/io/grpc/xds/ClientXdsClient.java
index 5c0952819d..b30048bc22 100644
--- a/xds/src/main/java/io/grpc/xds/ClientXdsClient.java
+++ b/xds/src/main/java/io/grpc/xds/ClientXdsClient.java
@@ -25,6 +25,7 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.CaseFormat;
 import com.google.common.base.Joiner;
 import com.google.common.base.Stopwatch;
+import com.google.common.base.Strings;
 import com.google.common.base.Supplier;
 import com.google.common.collect.ImmutableList;
 import com.google.protobuf.Any;
@@ -101,7 +102,8 @@ final class ClientXdsClient extends AbstractXdsClient {
   static final String HASH_POLICY_FILTER_STATE_KEY = "io.grpc.channel_id";
   @VisibleForTesting
   static boolean enableFaultInjection =
-      Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_FAULT_INJECTION"));
+      Strings.isNullOrEmpty(System.getenv("GRPC_XDS_EXPERIMENTAL_FAULT_INJECTION"))
+          || Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_FAULT_INJECTION"));
 
   private static final String TYPE_URL_HTTP_CONNECTION_MANAGER_V2 =
       "type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2"
diff --git a/xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java b/xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java
index a405e74bca..d00779a336 100644
--- a/xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java
+++ b/xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java
@@ -20,6 +20,7 @@ import static com.google.common.base.Preconditions.checkNotNull;
 import static io.grpc.xds.XdsSubchannelPickers.BUFFER_PICKER;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Strings;
 import io.grpc.Attributes;
 import io.grpc.ClientStreamTracer;
 import io.grpc.ClientStreamTracer.StreamInfo;
@@ -65,7 +66,8 @@ final class ClusterImplLoadBalancer extends LoadBalancer {
   static final long DEFAULT_PER_CLUSTER_MAX_CONCURRENT_REQUESTS = 1024L;
   @VisibleForTesting
   static boolean enableCircuitBreaking =
-      Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_CIRCUIT_BREAKING"));
+      Strings.isNullOrEmpty(System.getenv("GRPC_XDS_EXPERIMENTAL_CIRCUIT_BREAKING"))
+          || Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_CIRCUIT_BREAKING"));
   @VisibleForTesting
   static boolean enableSecurity =
       Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_SECURITY_SUPPORT"));
diff --git a/xds/src/main/java/io/grpc/xds/XdsNameResolver.java b/xds/src/main/java/io/grpc/xds/XdsNameResolver.java
index 91e0b4a38c..5861f09269 100644
--- a/xds/src/main/java/io/grpc/xds/XdsNameResolver.java
+++ b/xds/src/main/java/io/grpc/xds/XdsNameResolver.java
@@ -21,6 +21,7 @@ import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;
+import com.google.common.base.Strings;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Sets;
 import com.google.gson.Gson;
@@ -94,7 +95,8 @@ final class XdsNameResolver extends NameResolver {
       new NamedFilterConfig(null, LameFilter.LAME_CONFIG);
   @VisibleForTesting
   static boolean enableTimeout =
-      Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"));
+      Strings.isNullOrEmpty(System.getenv("GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"))
+          || Boolean.parseBoolean(System.getenv("GRPC_XDS_EXPERIMENTAL_ENABLE_TIMEOUT"));
 
   private final InternalLogId logId;
   private final XdsLogger logger;
diff --git a/xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java b/xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java
index 6d3cf01b7c..a0ae9e0037 100644
--- a/xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java
+++ b/xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java
@@ -305,16 +305,16 @@ public class ClusterImplLoadBalancerTest {
   }
 
   @Test
-  public void maxConcurrentRequests_appliedByLbConfig_enableCircuitBreaking() {
+  public void maxConcurrentRequests_appliedByLbConfig_disableCircuitBreaking() {
     boolean originalEnableCircuitBreaking = ClusterImplLoadBalancer.enableCircuitBreaking;
-    ClusterImplLoadBalancer.enableCircuitBreaking = true;
-    subtest_maxConcurrentRequests_appliedByLbConfig(true);
+    ClusterImplLoadBalancer.enableCircuitBreaking = false;
+    subtest_maxConcurrentRequests_appliedByLbConfig(false);
     ClusterImplLoadBalancer.enableCircuitBreaking = originalEnableCircuitBreaking;
   }
 
   @Test
-  public void maxConcurrentRequests_appliedByLbConfig_circuitBreakingDisabledByDefault() {
-    subtest_maxConcurrentRequests_appliedByLbConfig(false);
+  public void maxConcurrentRequests_appliedByLbConfig_circuitBreakingEnabledByDefault() {
+    subtest_maxConcurrentRequests_appliedByLbConfig(true);
   }
 
   private void subtest_maxConcurrentRequests_appliedByLbConfig(boolean enableCircuitBreaking) {
@@ -393,16 +393,16 @@ public class ClusterImplLoadBalancerTest {
   }
 
   @Test
-  public void maxConcurrentRequests_appliedWithDefaultValue_enableCircuitBreaking() {
+  public void maxConcurrentRequests_appliedWithDefaultValue_disableCircuitBreaking() {
     boolean originalEnableCircuitBreaking = ClusterImplLoadBalancer.enableCircuitBreaking;
-    ClusterImplLoadBalancer.enableCircuitBreaking = true;
-    subtest_maxConcurrentRequests_appliedWithDefaultValue(true);
+    ClusterImplLoadBalancer.enableCircuitBreaking = false;
+    subtest_maxConcurrentRequests_appliedWithDefaultValue(false);
     ClusterImplLoadBalancer.enableCircuitBreaking = originalEnableCircuitBreaking;
   }
 
   @Test
-  public void maxConcurrentRequests_appliedWithDefaultValue_circuitBreakingDisabledByDefault() {
-    subtest_maxConcurrentRequests_appliedWithDefaultValue(false);
+  public void maxConcurrentRequests_appliedWithDefaultValue_circuitBreakingEnabledByDefault() {
+    subtest_maxConcurrentRequests_appliedWithDefaultValue(true);
   }
 
   private void subtest_maxConcurrentRequests_appliedWithDefaultValue(