diff --git a/src/main/java/com/google/devtools/common/options/InvocationPolicyEnforcer.java b/src/main/java/com/google/devtools/common/options/InvocationPolicyEnforcer.java
index 42203a5..886793c 100644
--- a/src/main/java/com/google/devtools/common/options/InvocationPolicyEnforcer.java
+++ b/src/main/java/com/google/devtools/common/options/InvocationPolicyEnforcer.java
@@ -13,6 +13,7 @@
 // limitations under the License.
 package com.google.devtools.common.options;
 
+import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.stream.Collectors.joining;
 
 import com.google.common.base.Verify;
@@ -28,6 +29,7 @@
 import com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.FlagPolicy.OperationCase;
 import com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.InvocationPolicy;
 import com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.SetValue;
+import com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.SetValue.Behavior;
 import com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.UseDefault;
 import com.google.devtools.common.options.OptionPriority.PriorityCategory;
 import com.google.devtools.common.options.OptionsParser.OptionDescription;
@@ -119,6 +121,15 @@
       return;
     }
 
+    // TODO(b/186167747): Remove the warning once we migrate to the new enum.
+    invocationPolicy.getFlagPoliciesList().stream()
+        .filter(p -> p.hasSetValue() && p.getSetValue().getBehavior() == Behavior.UNDEFINED)
+        .findFirst()
+        .ifPresent(
+            policy ->
+                logger.atWarning().atMostEvery(5, MINUTES).log(
+                    "Invocation policy has missing/undefined behavior: %s", policy));
+
     // The effective policy returned is expanded, filtered for applicable commands, and cleaned of
     // redundancies and conflicts.
     List<FlagPolicyWithContext> effectivePolicies =