diff --git a/src/tt.cpp b/src/tt.cpp
index fcf70f628..359399347 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -110,9 +110,13 @@ void TTEntry::save(
     // Secondary aging. Important for elementary mate finding.
     // (*Scaler) Secondary aging on entries relevant to singular extensions
     // generally scales poorly and requires VVLTC verification.
-    else if (depth8 + DEPTH_NONE >= 5 && is_decisive(value16)
+    else if (depth8 + DEPTH_NONE >= 5
              && Bound((genBound8 & BOUND_MASK) >> BOUND_SHIFT) != BOUND_EXACT)
-        depth8--;
+    {
+        auto v16 = value16;
+        if (std::abs(v16) < VALUE_INFINITE && is_decisive(v16))
+            depth8--;
+    }
 }
 
 
diff --git a/tests/instrumented.py b/tests/instrumented.py
index dd84845ba..ed8b40c82 100644
--- a/tests/instrumented.py
+++ b/tests/instrumented.py
@@ -31,7 +31,7 @@ def get_prefix():
 
 def get_threads():
     if args.valgrind_thread or args.sanitizer_thread:
-        return 2
+        return 4
     return 1