diff --git a/src/lib/internal_functions.h b/src/lib/internal_functions.h
index aaf5e710..1827c4d9 100644
--- a/src/lib/internal_functions.h
+++ b/src/lib/internal_functions.h
@@ -110,7 +110,7 @@ static bool CompareOOVPAToAddress(iXbSymbolContext* pContext, OOVPA* Oovpa, memp
 // Return if the given (XRef'erenced) is not set yet.
 static inline bool internal_IsXRefUnset(uint16_t XRef)
 {
-    return (XRef == (uint16_t)XREF_ADDR_UNDETERMINED) || (XRef == XREF_ADDR_DERIVE);
+    return (XRef == XREF_UNDETERMINED) || (XRef <= XREF_KT_COUNT);
 }
 
 // Return if the given (XRef'erenced) address is not set yet.
diff --git a/src/lib/internal_tests.h b/src/lib/internal_tests.h
index bc712f47..e331970a 100644
--- a/src/lib/internal_tests.h
+++ b/src/lib/internal_tests.h
@@ -250,6 +250,12 @@ static unsigned int SymbolDatabaseVerifyContext_VerifyEntry(SymbolDatabaseVerify
         context->main.revision_index = revision_index;
 
         error_count += SymbolDatabaseVerifyContext_VerifyXRefJmp(context, table, symbol_index, revision_index);
+
+        // For safety check purpose
+        if (internal_IsXRefUnset(table[symbol_index].xref)) {
+            output_message_format(&context->output, XB_OUTPUT_MESSAGE_ERROR, "%s cannot have unset xref.", table[symbol_index].szFuncName);
+            error_count++;
+        }
     }
     else {
         context->against.symbol_index = symbol_index;
@@ -276,15 +282,6 @@ static unsigned int SymbolDatabaseVerifyContext_VerifyDatabase(SymbolDatabaseVer
 
     // Verify each entry in data's symbol table.
     for (uint32_t s = 0; s < data->SymbolsTableCount; s++) {
-        // We only need to check from main, not against.
-        if (context->against.data == NULL) {
-            // For safety check purpose
-            if (internal_IsXRefUnset(data->SymbolsTable[s].xref)) {
-                output_message_format(&context->output, XB_OUTPUT_MESSAGE_ERROR, "%s cannot have unset xref.", data->SymbolsTable[s].szFuncName);
-                error_count++;
-            }
-        }
-
         // Check each revision entry in a symbol.
         for (uint32_t r = 0; r < data->SymbolsTable[s].count; r++) {
             error_count += SymbolDatabaseVerifyContext_VerifyEntry(context, data->SymbolsTable, s, r);
diff --git a/src/xref/list_xref.h b/src/xref/list_xref.h
index cb23c267..1479dbee 100644
--- a/src/xref/list_xref.h
+++ b/src/xref/list_xref.h
@@ -418,7 +418,8 @@ typedef enum _XRefDatabaseOffset {
 #include "xonline.def"
 #undef XREF_SYMBOL
 
-    XREF_COUNT // XREF_COUNT must always be last.
+    XREF_COUNT, // XREF_COUNT must always be last.
+    XREF_UNDETERMINED = (uint16_t)-1
     // Also, if XREF_COUNT > sizeof(uint16), enlarge struct OOVPA.XRefSaveIndex (and Value somehow)
 } XRefDatabaseOffset;