diff --git a/java/com/google/gerrit/plugins/codeowners/restapi/CheckCodeOwnerConfigFiles.java b/java/com/google/gerrit/plugins/codeowners/restapi/CheckCodeOwnerConfigFiles.java
index b0da9f7..ae55e82 100644
--- a/java/com/google/gerrit/plugins/codeowners/restapi/CheckCodeOwnerConfigFiles.java
+++ b/java/com/google/gerrit/plugins/codeowners/restapi/CheckCodeOwnerConfigFiles.java
@@ -41,6 +41,7 @@
 import com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginConfiguration;
 import com.google.gerrit.plugins.codeowners.validation.CodeOwnerConfigValidator;
 import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
 import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.gerrit.server.permissions.PermissionBackendException;
@@ -54,6 +55,8 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevWalk;
 
 /**
  * REST endpoint that checks/validates the code owner config files in a project.
@@ -72,6 +75,7 @@
 
   private final Provider<CurrentUser> currentUser;
   private final PermissionBackend permissionBackend;
+  private final GitRepositoryManager repoManager;
   private final Provider<ListBranches> listBranches;
   private final CodeOwnersPluginConfiguration codeOwnersPluginConfiguration;
   private final CodeOwnerConfigScanner.Factory codeOwnerConfigScannerFactory;
@@ -81,12 +85,14 @@
   public CheckCodeOwnerConfigFiles(
       Provider<CurrentUser> currentUser,
       PermissionBackend permissionBackend,
+      GitRepositoryManager repoManager,
       Provider<ListBranches> listBranches,
       CodeOwnersPluginConfiguration codeOwnersPluginConfiguration,
       CodeOwnerConfigScanner.Factory codeOwnerConfigScannerFactory,
       CodeOwnerConfigValidator codeOwnerConfigValidator) {
     this.currentUser = currentUser;
     this.permissionBackend = permissionBackend;
+    this.repoManager = repoManager;
     this.listBranches = listBranches;
     this.codeOwnersPluginConfiguration = codeOwnersPluginConfiguration;
     this.codeOwnerConfigScannerFactory = codeOwnerConfigScannerFactory;
@@ -120,20 +126,23 @@
 
     validateInput(projectResource.getNameKey(), branches, input);
 
-    ImmutableMap.Builder<String, Map<String, List<ConsistencyProblemInfo>>> resultsByBranchBuilder =
-        ImmutableMap.builder();
-    branches.stream()
-        .filter(branchNameKey -> shouldValidateBranch(input, branchNameKey))
-        .filter(
-            branchNameKey ->
-                validateDisabledBranches(input)
-                    || !codeOwnersPluginConfiguration.isDisabled(branchNameKey))
-        .forEach(
-            branchNameKey ->
-                resultsByBranchBuilder.put(
-                    branchNameKey.branch(),
-                    checkBranch(input.path, branchNameKey, input.verbosity)));
-    return Response.ok(resultsByBranchBuilder.build());
+    try (Repository repo = repoManager.openRepository(projectResource.getNameKey());
+        RevWalk revWalk = new RevWalk(repo)) {
+      ImmutableMap.Builder<String, Map<String, List<ConsistencyProblemInfo>>>
+          resultsByBranchBuilder = ImmutableMap.builder();
+      branches.stream()
+          .filter(branchNameKey -> shouldValidateBranch(input, branchNameKey))
+          .filter(
+              branchNameKey ->
+                  validateDisabledBranches(input)
+                      || !codeOwnersPluginConfiguration.isDisabled(branchNameKey))
+          .forEach(
+              branchNameKey ->
+                  resultsByBranchBuilder.put(
+                      branchNameKey.branch(),
+                      checkBranch(revWalk, input.path, branchNameKey, input.verbosity)));
+      return Response.ok(resultsByBranchBuilder.build());
+    }
   }
 
   private ImmutableSet<BranchNameKey> branches(ProjectResource projectResource)
@@ -145,6 +154,7 @@
   }
 
   private Map<String, List<ConsistencyProblemInfo>> checkBranch(
+      RevWalk revWalk,
       String pathGlob,
       BranchNameKey branchNameKey,
       @Nullable ConsistencyProblemInfo.Status verbosity) {
@@ -162,7 +172,11 @@
               problemsByPath.putAll(
                   codeOwnerBackend.getFilePath(codeOwnerConfig.key()).toString(),
                   checkCodeOwnerConfig(
-                      branchNameKey.project(), codeOwnerBackend, codeOwnerConfig, verbosity));
+                      branchNameKey.project(),
+                      revWalk,
+                      codeOwnerBackend,
+                      codeOwnerConfig,
+                      verbosity));
               return true;
             },
             (codeOwnerConfigFilePath, configInvalidException) -> {
@@ -178,12 +192,17 @@
 
   private ImmutableList<ConsistencyProblemInfo> checkCodeOwnerConfig(
       Project.NameKey project,
+      RevWalk revWalk,
       CodeOwnerBackend codeOwnerBackend,
       CodeOwnerConfig codeOwnerConfig,
       @Nullable ConsistencyProblemInfo.Status verbosity) {
     return codeOwnerConfigValidator
         .validateCodeOwnerConfig(
-            project, currentUser.get().asIdentifiedUser(), codeOwnerBackend, codeOwnerConfig)
+            project,
+            revWalk,
+            currentUser.get().asIdentifiedUser(),
+            codeOwnerBackend,
+            codeOwnerConfig)
         .map(
             commitValidationMessage ->
                 createConsistencyProblemInfo(commitValidationMessage, verbosity))
diff --git a/java/com/google/gerrit/plugins/codeowners/validation/CodeOwnerConfigValidator.java b/java/com/google/gerrit/plugins/codeowners/validation/CodeOwnerConfigValidator.java
index cef6d52..2b8d479 100644
--- a/java/com/google/gerrit/plugins/codeowners/validation/CodeOwnerConfigValidator.java
+++ b/java/com/google/gerrit/plugins/codeowners/validation/CodeOwnerConfigValidator.java
@@ -488,7 +488,7 @@
         // issues. Hence in this case we downgrade all validation errors in the new version to
         // warnings so that the update is not blocked.
         return validateCodeOwnerConfig(
-                branchNameKey.project(), user, codeOwnerBackend, codeOwnerConfig)
+                branchNameKey.project(), revWalk, user, codeOwnerBackend, codeOwnerConfig)
             .map(CodeOwnerConfigValidator::downgradeErrorToWarning);
       }
 
@@ -500,13 +500,14 @@
     if (baseCodeOwnerConfig.isPresent()) {
       return validateCodeOwnerConfig(
           branchNameKey.project(),
+          revWalk,
           user,
           codeOwnerBackend,
           codeOwnerConfig,
           baseCodeOwnerConfig.get());
     }
     return validateCodeOwnerConfig(
-        branchNameKey.project(), user, codeOwnerBackend, codeOwnerConfig);
+        branchNameKey.project(), revWalk, user, codeOwnerBackend, codeOwnerConfig);
   }
 
   /**
@@ -672,6 +673,7 @@
    * they are not newly introduced by the given code owner config).
    *
    * @param project the name of the project
+   * @param revWalk rev walk that should be used to load the code owner configs
    * @param user user for which the code owner visibility checks should be performed
    * @param codeOwnerBackend the code owner backend from which the code owner configs were loaded
    * @param codeOwnerConfig the code owner config that should be validated
@@ -681,6 +683,7 @@
    */
   private Stream<CommitValidationMessage> validateCodeOwnerConfig(
       Project.NameKey project,
+      RevWalk revWalk,
       IdentifiedUser user,
       CodeOwnerBackend codeOwnerBackend,
       CodeOwnerConfig codeOwnerConfig,
@@ -689,9 +692,9 @@
     requireNonNull(baseCodeOwnerConfig, "baseCodeOwnerConfig");
 
     ImmutableSet<CommitValidationMessage> issuesInBaseVersion =
-        validateCodeOwnerConfig(project, user, codeOwnerBackend, baseCodeOwnerConfig)
+        validateCodeOwnerConfig(project, revWalk, user, codeOwnerBackend, baseCodeOwnerConfig)
             .collect(toImmutableSet());
-    return validateCodeOwnerConfig(project, user, codeOwnerBackend, codeOwnerConfig)
+    return validateCodeOwnerConfig(project, revWalk, user, codeOwnerBackend, codeOwnerConfig)
         .map(
             commitValidationMessage ->
                 issuesInBaseVersion.contains(commitValidationMessage)
@@ -703,6 +706,7 @@
    * Validates the given code owner config and returns validation issues as stream.
    *
    * @param project the name of the project
+   * @param revWalk rev walk that should be used to load the code owner configs from {@code project}
    * @param user user for which the code owner visibility checks should be performed
    * @param codeOwnerBackend the code owner backend from which the code owner config was loaded
    * @param codeOwnerConfig the code owner config that should be validated
@@ -711,6 +715,7 @@
    */
   public Stream<CommitValidationMessage> validateCodeOwnerConfig(
       Project.NameKey project,
+      RevWalk revWalk,
       IdentifiedUser user,
       CodeOwnerBackend codeOwnerBackend,
       CodeOwnerConfig codeOwnerConfig) {
@@ -719,7 +724,10 @@
         validateCodeOwnerReferences(
             project, user, codeOwnerBackend.getFilePath(codeOwnerConfig.key()), codeOwnerConfig),
         validateImports(
-            project, codeOwnerBackend.getFilePath(codeOwnerConfig.key()), codeOwnerConfig));
+            project,
+            revWalk,
+            codeOwnerBackend.getFilePath(codeOwnerConfig.key()),
+            codeOwnerConfig));
   }
 
   /**
@@ -796,6 +804,7 @@
    * Validates the imports of the given code owner config.
    *
    * @param project the name of the project
+   * @param revWalk rev walk that should be used to load the code owner configs from {@code project}
    * @param codeOwnerConfigFilePath the path of the code owner config file which contains the code
    *     owner config
    * @param codeOwnerConfig the code owner config for which the imports should be validated
@@ -803,13 +812,17 @@
    *     if there are no issues
    */
   private Stream<CommitValidationMessage> validateImports(
-      Project.NameKey project, Path codeOwnerConfigFilePath, CodeOwnerConfig codeOwnerConfig) {
+      Project.NameKey project,
+      RevWalk revWalk,
+      Path codeOwnerConfigFilePath,
+      CodeOwnerConfig codeOwnerConfig) {
     return Streams.concat(
             codeOwnerConfig.imports().stream()
                 .map(
                     codeOwnerConfigReference ->
                         validateCodeOwnerConfigReference(
                             project,
+                            revWalk,
                             codeOwnerConfigFilePath,
                             codeOwnerConfig.key(),
                             codeOwnerConfig.revision(),
@@ -821,6 +834,7 @@
                     codeOwnerConfigReference ->
                         validateCodeOwnerConfigReference(
                             project,
+                            revWalk,
                             codeOwnerConfigFilePath,
                             codeOwnerConfig.key(),
                             codeOwnerConfig.revision(),
@@ -834,6 +848,7 @@
    * Validates a code owner config reference.
    *
    * @param project the name of the project
+   * @param revWalk rev walk that should be used to load the code owner configs from {@code project}
    * @param codeOwnerConfigFilePath the path of the code owner config file which contains the code
    *     owner config reference
    * @param keyOfImportingCodeOwnerConfig key of the importing code owner config
@@ -846,6 +861,7 @@
    */
   private Optional<CommitValidationMessage> validateCodeOwnerConfigReference(
       Project.NameKey project,
+      RevWalk revWalk,
       Path codeOwnerConfigFilePath,
       CodeOwnerConfig.Key keyOfImportingCodeOwnerConfig,
       ObjectId codeOwnerConfigRevision,
@@ -916,9 +932,15 @@
     }
 
     try {
-      if (!codeOwnerBackend
-          .getCodeOwnerConfig(keyOfImportedCodeOwnerConfig, revision.get())
-          .isPresent()) {
+      // If a code owner config is imported from the same project, we must use the provided rev
+      // walk, otherwise the revision may not be visible yet and trying to load a code owner config
+      // from it could fail with MissingObjectException.
+      Optional<CodeOwnerConfig> importedCodeOwnerConfig =
+          keyOfImportedCodeOwnerConfig.project().equals(project)
+              ? codeOwnerBackend.getCodeOwnerConfig(
+                  keyOfImportedCodeOwnerConfig, revWalk, revision.get())
+              : codeOwnerBackend.getCodeOwnerConfig(keyOfImportedCodeOwnerConfig, revision.get());
+      if (!importedCodeOwnerConfig.isPresent()) {
         return nonResolvableImport(
             project,
             importType,
diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerConfigValidatorIT.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerConfigValidatorIT.java
index 0b55946..8d3c3cf 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerConfigValidatorIT.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnerConfigValidatorIT.java
@@ -1643,16 +1643,34 @@
   }
 
   private void testValidateMergeCommitCreatedViaTheCreateChangeRestApi() throws Exception {
+    skipTestIfImportsNotSupportedByCodeOwnersBackend();
+
     // Create another branch.
     String branchName = "stable";
     createBranch(BranchNameKey.create(project, branchName));
 
-    // Create a code owner config file in the other branch.
+    // Create a code owner config file in the other branch that can be imported.
+    CodeOwnerConfig.Key keyOfImportedCodeOwnerConfig =
+        codeOwnerConfigOperations
+            .newCodeOwnerConfig()
+            .project(project)
+            .branch(branchName)
+            .folderPath("/foo/")
+            .addCodeOwnerEmail(admin.email())
+            .create();
+
+    CodeOwnerConfigReference codeOwnerConfigReference =
+        CodeOwnerConfigReference.create(
+            CodeOwnerConfigImportMode.GLOBAL_CODE_OWNER_SETS_ONLY,
+            codeOwnerConfigOperations.codeOwnerConfig(keyOfImportedCodeOwnerConfig).getFilePath());
+
+    // Create a code owner config file in the other branch that contains an import.
     codeOwnerConfigOperations
         .newCodeOwnerConfig()
         .project(project)
         .branch(branchName)
         .folderPath("/")
+        .addImport(codeOwnerConfigReference)
         .addCodeOwnerEmail(user.email())
         .create();