diff --git a/src/main/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStep.java b/src/main/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStep.java
index 11b70e8a..d724ab84 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStep.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStep.java
@@ -39,6 +39,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import jenkins.scm.api.SCMHead;
 import jenkins.scm.api.SCMHeadObserver;
@@ -90,6 +91,10 @@ public class ResolveScmStep extends Step {
     @DataBoundConstructor
     public ResolveScmStep(@NonNull SCMSource source, @NonNull List<String> targets) {
         this.source = source;
+        // JENKINS-67005: Pipeline passes null when targets is omitted from the step call.
+        Objects.requireNonNull(
+                targets,
+                "targets is required; provide candidate branch names, e.g. targets: [env.BRANCH_NAME, 'main']");
         this.targets = new ArrayList<>(targets);
     }
 
diff --git a/src/test/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStepTest.java b/src/test/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStepTest.java
index b339ea9f..75120e7e 100644
--- a/src/test/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStepTest.java
+++ b/src/test/java/org/jenkinsci/plugins/workflow/multibranch/ResolveScmStepTest.java
@@ -25,10 +25,12 @@
 
 package org.jenkinsci.plugins.workflow.multibranch;
 
+import hudson.model.Result;
 import hudson.model.TopLevelItem;
 import jenkins.scm.impl.mock.MockSCMController;
 import org.jenkinsci.plugins.workflow.cps.CpsFlowDefinition;
 import org.jenkinsci.plugins.workflow.job.WorkflowJob;
+import org.jenkinsci.plugins.workflow.job.WorkflowRun;
 import org.junit.Before;
 import org.junit.ClassRule;
 import org.junit.Test;
@@ -121,4 +123,20 @@ public void given_nonExistingHeadName_when_invokedWithDefault_then_defaultReturn
             j.buildAndAssertSuccess(job);
         }
     }
+
+    @Test
+    public void given_targetsOmitted_when_invoked_then_failsWithClearMessage() throws Exception {
+        try (MockSCMController c = MockSCMController.create()) {
+            c.createRepository("repo");
+            WorkflowJob job = j.jenkins.createProject(WorkflowJob.class, "workflow");
+            job.setDefinition(new CpsFlowDefinition("node {\n"
+                    + "  resolveScm source: mockScm(controllerId:'"
+                    + c.getId()
+                    + "', repository:'repo', traits: [discoverBranches()])\n"
+                    + "}", true));
+            WorkflowRun b = j.assertBuildStatus(Result.FAILURE, job.scheduleBuild2(0));
+            j.assertLogContains("targets is required", b);
+        }
+    }
+
 }