diff --git a/java/com/google/gerrit/server/IdentifiedUser.java b/java/com/google/gerrit/server/IdentifiedUser.java
index 1b729d04ce..b007fc0f26 100644
--- a/java/com/google/gerrit/server/IdentifiedUser.java
+++ b/java/com/google/gerrit/server/IdentifiedUser.java
@@ -301,6 +301,11 @@ public class IdentifiedUser extends CurrentUser {
     return state().getUserName().orElse(null);
   }
 
+  /** @return unique name of the user for logging, never {@code null} */
+  public String getLoggableName() {
+    return getUserName() != null ? getUserName() : "a/" + getAccountId().get();
+  }
+
   public Account getAccount() {
     return state().getAccount();
   }
diff --git a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
index 611c5cf819..03090faca9 100644
--- a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
+++ b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
@@ -918,7 +918,7 @@ class ReceiveCommits {
                 reject(cmd, "invalid project configuration");
                 logError(
                     "User "
-                        + user.getUserName()
+                        + user.getLoggableName()
                         + " tried to push invalid project configuration "
                         + cmd.getNewId().name()
                         + " for "
@@ -994,7 +994,7 @@ class ReceiveCommits {
               reject(cmd, "invalid project configuration");
               logError(
                   "User "
-                      + user.getUserName()
+                      + user.getLoggableName()
                       + " tried to push invalid project configuration "
                       + cmd.getNewId().name()
                       + " for "
diff --git a/java/com/google/gerrit/server/git/validators/CommitValidators.java b/java/com/google/gerrit/server/git/validators/CommitValidators.java
index 05ca98bfb0..b438c0a2b8 100644
--- a/java/com/google/gerrit/server/git/validators/CommitValidators.java
+++ b/java/com/google/gerrit/server/git/validators/CommitValidators.java
@@ -447,7 +447,7 @@ public class CommitValidators {
         } catch (ConfigInvalidException | IOException e) {
           log.error(
               "User "
-                  + user.getUserName()
+                  + user.getLoggableName()
                   + " tried to push an invalid project configuration "
                   + receiveEvent.command.getNewId().name()
                   + " for project "