diff --git a/modules/core/src/system.cpp b/modules/core/src/system.cpp
index 5fbb453742..768280e1a6 100644
--- a/modules/core/src/system.cpp
+++ b/modules/core/src/system.cpp
@@ -1085,11 +1085,14 @@ public:
 
         for(size_t i = 0; i < threads.size(); i++)
         {
-            std::vector<void*>& thread_slots = threads[i]->slots;
-            if (thread_slots.size() > slotIdx && thread_slots[slotIdx])
+            if(threads[i])
             {
-                dataVec.push_back(thread_slots[slotIdx]);
-                threads[i]->slots[slotIdx] = 0;
+                std::vector<void*>& thread_slots = threads[i]->slots;
+                if (thread_slots.size() > slotIdx && thread_slots[slotIdx])
+                {
+                    dataVec.push_back(thread_slots[slotIdx]);
+                    threads[i]->slots[slotIdx] = 0;
+                }
             }
         }
 
@@ -1116,9 +1119,12 @@ public:
 
         for(size_t i = 0; i < threads.size(); i++)
         {
-            std::vector<void*>& thread_slots = threads[i]->slots;
-            if (thread_slots.size() > slotIdx && thread_slots[slotIdx])
-                dataVec.push_back(thread_slots[slotIdx]);
+            if(threads[i])
+            {
+                std::vector<void*>& thread_slots = threads[i]->slots;
+                if (thread_slots.size() > slotIdx && thread_slots[slotIdx])
+                    dataVec.push_back(thread_slots[slotIdx]);
+            }
         }
     }