diff --git a/src/acl.c b/src/acl.c
index 43517300..991be210 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -931,9 +931,16 @@ int ACLCheckCommandPerm(client *c) {
  *
  * Note that this function cannot stop in case of commands that are not found
  * and, in that case, the error will be emitted later, because certain
- * commands may be defined later once modules are loaded. */
-int ACLAppendUserForLoading(sds *argv, int argc) {
-    if (argc < 2 || strcasecmp(argv[0],"user")) return C_ERR;
+ * commands may be defined later once modules are loaded.
+ *
+ * When an error is detected and C_ERR is returned, the function populates
+ * by reference (if not set to NULL) the argc_err argument with the index
+ * of the argv vector that caused the error. */
+int ACLAppendUserForLoading(sds *argv, int argc, int *argc_err) {
+    if (argc < 2 || strcasecmp(argv[0],"user")) {
+        if (argc_err) *argc_err = 0;
+        return C_ERR;
+    }
 
     /* Try to apply the user rules in a fake user to see if they
      * are actually valid. */
@@ -947,6 +954,7 @@ int ACLAppendUserForLoading(sds *argv, int argc) {
         if (ACLSetUser(fakeuser,argv[j],sdslen(argv[j])) == C_ERR) {
             if (errno != ENOENT) {
                 ACLFreeUser(fakeuser);
+                if (argc_err) *argc_err = j;
                 return C_ERR;
             }
         }
diff --git a/src/config.c b/src/config.c
index b2600d2e..c852b01b 100644
--- a/src/config.c
+++ b/src/config.c
@@ -792,7 +792,8 @@ void loadServerConfigFromString(char *config) {
                 goto loaderr;
             }
         } else if (!strcasecmp(argv[0],"user") && argc >= 2) {
-            if (ACLAppendUserForLoading(argv,argc) == C_ERR) {
+            int argc_err;
+            if (ACLAppendUserForLoading(argv,argc,&argc_err) == C_ERR) {
                 err = "Syntax error in user declaration";
                 goto loaderr;
             }
diff --git a/src/server.h b/src/server.h
index 3f23cee2..cbf995d4 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1738,7 +1738,7 @@ int ACLCheckCommandPerm(client *c);
 int ACLSetUser(user *u, const char *op, ssize_t oplen);
 sds ACLDefaultUserFirstPassword(void);
 uint64_t ACLGetCommandCategoryFlagByName(const char *name);
-int ACLAppendUserForLoading(sds *argv, int argc);
+int ACLAppendUserForLoading(sds *argv, int argc, int *argc_err);
 
 /* Sorted sets data type */