diff --git a/test_regress/t/t_trace_litendian.pl b/test_regress/t/t_trace_litendian.pl
index a706f79f3..6c009db98 100755
--- a/test_regress/t/t_trace_litendian.pl
+++ b/test_regress/t/t_trace_litendian.pl
@@ -10,8 +10,12 @@ if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); di
 
 scenarios(simulator => 1);
 
+# Travis environment offers 2 VCPUs, 2 thread setting causes the following warning.
+# %Warning-UNOPTTHREADS: Thread scheduler is unable to provide requested parallelism; consider asking for fewer threads.
+# Strangely, asking for more threads makes it go away.
 compile(
-    verilator_flags2 => ['--cc --trace --trace-params -Wno-LITENDIAN'],
+    verilator_flags2 => ['--cc --trace --trace-params -Wno-LITENDIAN',
+                        ($Self->{vltmt} ? '--threads 6' : '')],
     );
 
 execute(
diff --git a/test_regress/t/t_trace_litendian_fst.pl b/test_regress/t/t_trace_litendian_fst.pl
index d9a4056cb..b21f65f85 100755
--- a/test_regress/t/t_trace_litendian_fst.pl
+++ b/test_regress/t/t_trace_litendian_fst.pl
@@ -12,8 +12,12 @@ scenarios(simulator => 1);
 
 top_filename("t/t_trace_litendian.v");
 
+# Travis environment offers 2 VCPUs, 2 thread setting causes the following warning.
+# %Warning-UNOPTTHREADS: Thread scheduler is unable to provide requested parallelism; consider asking for fewer threads.
+# Strangely, asking for more threads makes it go away.
 compile(
-    verilator_flags2 => ['--cc --trace-fst --trace-params -Wno-LITENDIAN'],
+    verilator_flags2 => ['--cc --trace-fst --trace-params -Wno-LITENDIAN',
+                        ($Self->{vltmt} ?  '--threads 6' : '')],
     );
 
 execute(