diff --git a/symbol/symbol.cpp b/symbol/symbol.cpp
index e30b5a3a4d27d519d7d3a75ae56f8aee670ec63a..699dca8ae437bbf0f0353fb52bdf6fc6a6968edb 100644
--- a/symbol/symbol.cpp
+++ b/symbol/symbol.cpp
@@ -79,7 +79,7 @@ void SymResolverDestroy()
     SymbolResolve::GetInstance()->Clear();
 }
 
-struct Stack*  StackToHash(int pid, unsigned long* stack, int nr)
+struct Stack* StackToHash(int pid, unsigned long* stack, int nr)
 {
     try {
         return SymbolResolve::GetInstance()->StackToHash(pid, stack, nr);
diff --git a/symbol/symbol_resolve.cpp b/symbol/symbol_resolve.cpp
index 504e526b43ae1ee80f55bbf3db1a3886eda13c0b..eb9042d54e1ebf465d188ab606882663e16db023 100644
--- a/symbol/symbol_resolve.cpp
+++ b/symbol/symbol_resolve.cpp
@@ -61,6 +61,7 @@ const std::string R_XP = "r-xp";
 const std::string SLASH = "/";
 const char DASH = '-';
 const char EXE_TYPE = 'x';
+char* UNKNOWN = "UNKNOWN";
 
 namespace {
     static inline void SetFalse(bool& flag)
@@ -90,6 +91,16 @@ namespace {
         return str;
     }
 
+    static inline Symbol* InitializeSymbol(unsigned long addr) {
+        struct Symbol* symbol = new struct Symbol();
+        symbol->module = UNKNOWN;
+        symbol->symbolName = UNKNOWN;
+        symbol->fileName = UNKNOWN;
+        symbol->addr = addr;
+        symbol->offset = 0;
+        return symbol;
+    }
+
     static void ReadProcPidMap(std::ifstream& file, std::vector<std::shared_ptr<ModuleMap>>& modVec)
     {
         char line[MAX_LINUX_SYMBOL_LEN];
@@ -269,15 +280,15 @@ namespace {
 
 void SymbolUtils::FreeSymbol(struct Symbol* symbol)
 {
-    if (symbol->symbolName) {
+    if (symbol->symbolName && symbol->symbolName != UNKNOWN) {
         delete[] symbol->symbolName;
         symbol->symbolName = nullptr;
     }
-    if (symbol->fileName) {
+    if (symbol->fileName && symbol->fileName != UNKNOWN) {
         delete[] symbol->fileName;
         symbol->fileName = nullptr;
     }
-    if (symbol->module) {
+    if (symbol->module && symbol->fileName != UNKNOWN) {
         delete[] symbol->module;
         symbol->module = nullptr;
     }
@@ -815,7 +826,7 @@ struct Stack* SymbolResolve::StackToHash(int pid, unsigned long* stack, int nr)
         if (symbol != nullptr) {
             current->symbol = symbol;
         } else {
-            current->symbol = nullptr;
+            current->symbol = InitializeSymbol(stack[i]);
         }
         AddDoubleLinkedTail<struct Stack>(&head, &current);
     }