diff --git a/test/run-tests.py b/test/run-tests.py
index 6f77f53..ebb8a9b 100755
--- a/test/run-tests.py
+++ b/test/run-tests.py
@@ -6,7 +6,7 @@
 passed, failed, verbose, quiet = 0, 0, 0, 0
 
 def run (forthfile):
-    return os.popen ("gforth ../ttester-codewars.4th " + forthfile + " -e bye").readlines ()
+    return os.popen ("bash -c 'gforth ../ttester-codewars.4th " + forthfile + " -e bye 2> >(sed -E \"s/redefined [^ ]+  //g\" >&2)'").readlines ()
 
 def timeless (lines):
     return [re.sub(r'\d+', '0', l) if "<COMPLETEDIN::>" in l else l for l in lines]
diff --git a/test/test-stack-underflow.4th b/test/test-stack-underflow.4th
new file mode 100644
index 0000000..1b3aa54
--- /dev/null
+++ b/test/test-stack-underflow.4th
@@ -0,0 +1,18 @@
+\ Copyright 2019 nomennescio
+s" stack underflow" describe#{
+  s" single test" it#{
+    <{ drop -> 0 }>
+  }#
+  s" double test" it#{
+    <{ drop -> 0 }>
+    <{ drop drop -> 0 }>
+  }#
+  s" double test" it#{
+    <{ drop -> 0 0 }>
+    <{ drop drop -> 0 0 }>
+  }#
+  s" double test" it#{
+    <{ drop -> 0 0 }>
+    <{ drop drop -> 0 }>
+  }#
+}#
diff --git a/test/test-stack-underflow.expected b/test/test-stack-underflow.expected
new file mode 100644
index 0000000..aeab6a5
--- /dev/null
+++ b/test/test-stack-underflow.expected
@@ -0,0 +1,34 @@
+
+<DESCRIBE::>stack underflow
+
+<IT::>single test
+
+<FAILED::>Wrong number of results, expected 1 , got a 1 cell stack underflow
+
+<COMPLETEDIN::>0.033 ms
+
+<IT::>double test
+
+<FAILED::>Wrong number of results, expected 1 , got a 1 cell stack underflow
+
+<FAILED::>Wrong number of results, expected 1 , got a 2 cell stack underflow
+
+<COMPLETEDIN::>1565296144893.672 ms
+
+<IT::>double test
+
+<FAILED::>Wrong number of results, expected 2 , got a 1 cell stack underflow
+
+<FAILED::>Wrong number of results, expected 2 , got a 2 cell stack underflow
+
+<COMPLETEDIN::>1565296144893.759 ms
+
+<IT::>double test
+
+<FAILED::>Wrong number of results, expected 2 , got a 1 cell stack underflow
+
+<FAILED::>Wrong number of results, expected 1 , got a 2 cell stack underflow
+
+<COMPLETEDIN::>1565296144893.836 ms
+
+<COMPLETEDIN::>0.311 ms
diff --git a/ttester-codewars.4th b/ttester-codewars.4th
index 8553ffb..3ad39b4 100644
--- a/ttester-codewars.4th
+++ b/ttester-codewars.4th
@@ -2,10 +2,10 @@
 decimal
 s" test/ttester.fs" included
 
-: #ms ( dmicroseconds -- len c-addr ) <# # # # [char] . hold #s #> ;
+: #ms ( dmicroseconds -- c-addr len ) <# # # # [char] . hold #s #> ;
 
-: describe#{ ( len c-addr -- ) cr ." <DESCRIBE::>" type cr utime ;
-: it#{ ( len c-addr -- ) cr ." <IT::>" type cr utime ;
+: describe#{ ( c-addr len -- ) cr ." <DESCRIBE::>" type cr utime ;
+: it#{ ( c-addr len -- ) cr ." <IT::>" type cr utime ;
 : }# ( -- ) utime cr ." <COMPLETEDIN::>" 2swap d- #ms type ."  ms" cr ;
 
 : failed# ( -- ) cr ." <FAILED::>" ;
@@ -26,13 +26,20 @@ variable ^different
   RESULTS @ 0 +do ACTUAL-RESULTS i cells + @ . loop
   cr ;
 : nresults$ ." Wrong number of results, expected " depth START-DEPTH @ - .
-  ." , got " ACTUAL-DEPTH @ START-DEPTH @ - . cr ;
+  ." , got " ACTUAL-DEPTH @ START-DEPTH @ - dup 0< if negate ." a " . ." cell stack underflow" else . then cr ;
 
 ' passed$ ^passed !
 ' nresults$ ^nresults !
 ' different$ ^different !
 
 : <{ T{ ;
+: ->  depth dup ACTUAL-DEPTH !
+   START-DEPTH @ >= if
+     depth START-DEPTH @ - 0 +do ACTUAL-RESULTS i cells + ! loop
+   else
+     START-DEPTH @ depth - -1 +do 0 loop
+   then
+   F-> ;
 : }>
   depth ACTUAL-DEPTH @ = if
     depth START-DEPTH @ > if
@@ -56,4 +63,4 @@ variable ^different
 3037000493 constant #m \ prime number < sqrt (2^63-1)
 53 constant #p         \ prime number
 : c# { hash pow c -- hash' pow' } c pow * hash + #m mod pow #p * #m mod ;       \ polynomial rolling hash function, single char
-: s# { c-addr u -- hash } 0 1 c-addr u 0 +do { s } s c@ c# s char+ loop 2drop ; \ string hash
\ No newline at end of file
+: s# { c-addr len -- hash } 0 1 c-addr len 0 +do { s } s c@ c# s char+ loop 2drop ; \ string hash
\ No newline at end of file