diff --git a/wally-pipelined/regression/regression-wally.py b/wally-pipelined/regression/regression-wally.py
index f97202d4..531d0e8c 100755
--- a/wally-pipelined/regression/regression-wally.py
+++ b/wally-pipelined/regression/regression-wally.py
@@ -9,27 +9,37 @@
 ##################################
 
 # edit this line to add more configurations
-confignames = ["rv32ic", "rv64ic"]
+confignames = ["rv32ic", "rv64ic", "busybear"]
 
 import multiprocessing, os
 
 fail = 0
 
+def search_log_for_text(text, logfile):
+    """Search through the given log file for text, returning True if it is found or False if it is not"""
+    grepcmd = "grep -e '%s' '%s' > /dev/null" % (text, logfile)
+    return os.system(grepcmd) == 0
+
 def test_config(config, print_res=True):
   """Run the given config, and return 0 if it suceeds and 1 if it fails"""
   logname = "wally_"+config+".log"
-  cmd = "vsim -c >" + logname +" <<!\ndo wally-pipelined-batch-parallel.do ../config/" + config + " " + config + "\n!\n"
-  os.system(cmd)
-
-  # check for success.  grep returns 0 if found, 1 if not found
-  cmd = "grep 'All tests ran without failures' " + logname + "> /dev/null"
-  grepval = os.system(cmd)
-  if (grepval):
-    if print_res:print(logname+": failures detected")
-    return 1
+  if config == "busybear":
+    cmd = "echo 'quit' | vsim -do wally-busybear.do -c >" + logname
+    os.system(cmd)
+    # check for success.  grep returns 0 if found, 1 if not found
+    passed = search_log_for_text("no more .* to read", logname)
   else:
+    cmd = "vsim -c >" + logname +" <<!\ndo wally-pipelined-batch-parallel.do ../config/" + config + " " + config + "\n!\n"
+    os.system(cmd)
+    # check for success.  grep returns 0 if found, 1 if not found
+    passed = search_log_for_text("All tests ran without failures", logname)
+  if passed:
     if print_res:print(logname+": Success")
     return 0
+  else:
+    if print_res:print(logname+": failures detected")
+    return 1
+
 
 pool = multiprocessing.Pool(min(len(confignames), 12))
 fail = sum(pool.map(test_config, confignames))
diff --git a/wally-pipelined/src/ieu/extend.sv b/wally-pipelined/src/ieu/extend.sv
index ec144a3a..243dced3 100644
--- a/wally-pipelined/src/ieu/extend.sv
+++ b/wally-pipelined/src/ieu/extend.sv
@@ -42,8 +42,6 @@ module extend (
       3'b011:   ExtImmD = {{(`XLEN-20){InstrD[31]}}, InstrD[19:12], InstrD[20], InstrD[30:21], 1'b0}; 
                // U-type (lui, auipc)
       3'b100:  ExtImmD = {{(`XLEN-31){InstrD[31]}}, InstrD[30:12], 12'b0}; 
-      /* verilator lint_off WIDTH */
-      default: ExtImmD = 'bx; // undefined
-      /* verilator lint_on WIDTH */
+      default: ExtImmD = {(`XLEN-1){1'bx}}; // undefined
     endcase             
 endmodule