diff --git a/core/front/tiny_unified_cache.c b/core/front/tiny_unified_cache.c
index dbf55293..6aedf0e9 100644
--- a/core/front/tiny_unified_cache.c
+++ b/core/front/tiny_unified_cache.c
@@ -350,7 +350,10 @@ void* unified_cache_refill(int class_idx) {
     if (produced == 0) return NULL;
 
     // Step 4: Update active counter
-    ss_active_add(tls->ss, (uint32_t)produced);
+    // Guard: tls->ss can be NULL if all SuperSlab refills failed
+    if (tls->ss) {
+        ss_active_add(tls->ss, (uint32_t)produced);
+    }
 
     // Step 5: Store blocks into unified cache (skip first, return it)
     void* first = out[0];