diff --git a/CHANGELOG.md b/CHANGELOG.md
index 59e722440..30b502418 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 - Also create owner WITH clause for single resources [#1406](https://github.com/greenbone/gvmd/pull/1406)
 - Fix SQL escaping when adding VT references [#1429](https://github.com/greenbone/gvmd/pull/1429)
+- Improve modify_override errors, fix no NVT case [#1435](https://github.com/greenbone/gvmd/pull/1435)
 
 ### Removed
 
diff --git a/src/gmp.c b/src/gmp.c
index e05580d2e..237c447b5 100644
--- a/src/gmp.c
+++ b/src/gmp.c
@@ -23804,6 +23804,38 @@ gmp_xml_handle_end_element (/* unused */ GMarkupParseContext* context,
                                 modify_override_data->override_id,
                                 "modified");
                 break;
+              case 8:
+                SEND_TO_CLIENT_OR_FAIL
+                 (XML_ERROR_SYNTAX ("modify_override",
+                                    "Error in threat specification"));
+                log_event_fail ("override", "Override",
+                                modify_override_data->override_id,
+                                "modified");
+                break;
+              case 9:
+                SEND_TO_CLIENT_OR_FAIL
+                 (XML_ERROR_SYNTAX ("modify_override",
+                                    "Error in new_threat specification"));
+                log_event_fail ("override", "Override",
+                                modify_override_data->override_id,
+                                "modified");
+                break;
+              case 10:
+                SEND_TO_CLIENT_OR_FAIL
+                 (XML_ERROR_SYNTAX ("modify_override",
+                                    "Error in new_severity specification"));
+                log_event_fail ("override", "Override",
+                                modify_override_data->override_id,
+                                "modified");
+                break;
+              case 11:
+                SEND_TO_CLIENT_OR_FAIL
+                 (XML_ERROR_SYNTAX ("modify_override",
+                                    "new_severity is required"));
+                log_event_fail ("override", "Override",
+                                modify_override_data->override_id,
+                                "modified");
+                break;
               case -1:
                 SEND_TO_CLIENT_OR_FAIL
                  (XML_INTERNAL_ERROR ("modify_override"));
diff --git a/src/manage_sql.c b/src/manage_sql.c
index 49a30b4b6..2cf28a36f 100644
--- a/src/manage_sql.c
+++ b/src/manage_sql.c
@@ -37583,7 +37583,9 @@ delete_override (const char *override_id, int ultimate)
  *
  * @return 0 success, -1 error, 1 syntax error in active, 2 invalid port,
  *         3 invalid severity score, 4 failed to find NVT, 5 failed to find
- *         override, 6 failed to find task, 7 failed to find result.
+ *         override, 6 failed to find task, 7 failed to find result,
+ *         8 invalid threat, 9 invalid new_threat, 10 invalid new_severity,
+ *         11 missing new_severity.
  */
 int
 modify_override (const gchar *override_id, const char *active, const char *nvt,
@@ -37643,18 +37645,6 @@ modify_override (const gchar *override_id, const char *active, const char *nvt,
   if (nvt && !nvt_exists (nvt))
     return 4;
 
-  if (threat && strcmp (threat, "High") && strcmp (threat, "Medium")
-      && strcmp (threat, "Low") && strcmp (threat, "Log")
-      && strcmp (threat, "Debug") && strcmp (threat, "Alarm")
-      && strcmp (threat, ""))
-    return -1;
-
-  if (new_threat && strcmp (new_threat, "High") && strcmp (new_threat, "Medium")
-      && strcmp (new_threat, "Low") && strcmp (new_threat, "Log")
-      && strcmp (new_threat, "Debug") && strcmp (new_threat, "False Positive")
-      && strcmp (new_threat, "Alarm") && strcmp (new_threat, ""))
-    return -1;
-
   severity_dbl = 0.0;
   if (severity != NULL && strcmp (severity, ""))
     {
@@ -37680,7 +37670,7 @@ modify_override (const gchar *override_id, const char *active, const char *nvt,
       else if (strcmp (threat, "Debug") == 0)
         severity_dbl = SEVERITY_DEBUG;
       else
-        return -1;
+        return 8;
 
       quoted_severity = g_strdup_printf ("'%1.1f'", severity_dbl);
     }
@@ -37697,7 +37687,7 @@ modify_override (const gchar *override_id, const char *active, const char *nvt,
               && new_severity_dbl != SEVERITY_DEBUG))
         {
           g_free (quoted_severity);
-          return 3;
+          return 10;
         }
     }
   else if (new_threat != NULL && strcmp (new_threat, ""))
@@ -37717,19 +37707,19 @@ modify_override (const gchar *override_id, const char *active, const char *nvt,
       else
         {
           g_free (quoted_severity);
-          return -1;
+          return 9;
         }
     }
   else
     {
       g_free (quoted_severity);
-      return -1;
+      return 11;
     }
 
   quoted_text = sql_insert (text);
   quoted_hosts = sql_insert (hosts);
   quoted_port = sql_insert (port);
-  quoted_nvt = sql_quote (nvt);
+  quoted_nvt = nvt ? sql_quote (nvt) : NULL;
 
   // Tests if a cache rebuild is necessary.
   //  The "active" status is checked separately