diff --git a/include/verilated_threads.cpp b/include/verilated_threads.cpp
index 96911eda6..cf503fda9 100644
--- a/include/verilated_threads.cpp
+++ b/include/verilated_threads.cpp
@@ -156,7 +156,7 @@ std::string VlThreadPool::numaAssign() {
     // Make a reasonable processor affinity selection
     const int num_threads = static_cast<int>(m_workers.size());
     if (num_threads < 2) return "too few threads";
-    if (static_cast<unsigned>(num_threads) > num_proc) return "too many threads";
+    if (static_cast<unsigned>(num_threads) >= num_proc - 1) return "too many threads";
 
     // Read CPU info.
     // Uncertain if any modern system has gaps in the processor id (Solaris
diff --git a/test_regress/t/t_gantt_numa.py b/test_regress/t/t_gantt_numa.py
index a58c53bda..87f1f1f10 100755
--- a/test_regress/t/t_gantt_numa.py
+++ b/test_regress/t/t_gantt_numa.py
@@ -41,7 +41,8 @@ for trial in range(0, trials):
 
     if sys.platform != "darwin":
         test.file_grep(gantt_log, r'CPU info:')
-        test.file_grep(gantt_log, r'NUMA status += (assigned|%Warning: no /proc/cpuinfo)')
+        test.file_grep(gantt_log,
+                       r'NUMA status += (assigned|too many threads|%Warning: no /proc/cpuinfo)')
         # False fails occasionally
         # test.file_grep_not(gantt_log, r'%Warning:')  # e.g. There were fewer CPUs (1) than threads (3).