diff --git a/src/tm-threads.c b/src/tm-threads.c
index b21770e4ea..1d7b5fe149 100644
--- a/src/tm-threads.c
+++ b/src/tm-threads.c
@@ -2283,7 +2283,7 @@ int TmThreadsRegisterThread(ThreadVars *tv, const int type)
     void *newmem = SCRealloc(thread_store.threads, ((thread_store.threads_size + STEP) * sizeof(Thread)));
     BUG_ON(newmem == NULL);
     thread_store.threads = newmem;
-    memset((uint8_t *)thread_store.threads + (thread_store.threads_size * sizeof(Thread)), 0x00, STEP);
+    memset((uint8_t *)thread_store.threads + (thread_store.threads_size * sizeof(Thread)), 0x00, STEP * sizeof(Thread));
 
     Thread *t = &thread_store.threads[thread_store.threads_size];
     t->name = tv->name;