diff --git a/bin/verilator_difftree b/bin/verilator_difftree
index 8583c2e7f..992af1569 100755
--- a/bin/verilator_difftree
+++ b/bin/verilator_difftree
@@ -92,8 +92,10 @@ sub diff_file {
     my $a = shift;
     my $b = shift;
     # Compare the two tree files
-    my $tmp_a = "/tmp/$$.a";
-    my $tmp_b = "/tmp/$$.b";
+    (my $short_a = $a) =~ s/[^a-zA-Z0-9.]+/_/g;
+    (my $short_b = $b) =~ s/[^a-zA-Z0-9.]+/_/g;
+    my $tmp_a = "/tmp/${$}_${short_a}.a";
+    my $tmp_b = "/tmp/${$}_${short_b}.b";
 
     my $vera = version_from($a);
     my $verb = version_from($b);
diff --git a/test_regress/driver.pl b/test_regress/driver.pl
index 4862a0045..57c0cb81c 100755
--- a/test_regress/driver.pl
+++ b/test_regress/driver.pl
@@ -204,7 +204,7 @@ sub usage {
 
 sub debug {
     $Debug = 1;
-    push @Opt_Driver_Verilator_Flags, "--debug";
+    push @Opt_Driver_Verilator_Flags, "--debug --no-skip-identical";
 }
 
 our $_Parameter_Next_Level;