diff --git a/mysql-test/lib/mtr_io.pl b/mysql-test/lib/mtr_io.pl
index 984d834486c..09749bc74e3 100644
--- a/mysql-test/lib/mtr_io.pl
+++ b/mysql-test/lib/mtr_io.pl
@@ -13,6 +13,8 @@ sub mtr_tofile ($@);
 sub mtr_tonewfile($@);
 sub mtr_lastlinefromfile($);
 sub mtr_appendfile_to_file ($$);
+sub mtr_grab_file($);
+
 
 ##############################################################################
 #
@@ -128,6 +130,7 @@ sub unspace {
   return "$quote$string$quote";
 }
 
+# Read a whole file, stripping leading and trailing whitespace.
 sub mtr_fromfile ($) {
   my $file=  shift;
 
@@ -181,5 +184,16 @@ sub mtr_appendfile_to_file ($$) {
   close TOFILE;
 }
 
+# Read a whole file verbatim.
+sub mtr_grab_file($) {
+  my $file= shift;
+  open(FILE, '<', $file)
+    or return undef;
+  local $/= undef;
+  my $data= scalar(<FILE>);
+  close FILE;
+  return $data;
+}
+
 
 1;
diff --git a/mysql-test/mysql-test-run.pl b/mysql-test/mysql-test-run.pl
index 0da28d79e56..8a1d9b50f47 100755
--- a/mysql-test/mysql-test-run.pl
+++ b/mysql-test/mysql-test-run.pl
@@ -1603,9 +1603,17 @@ sub environment_setup () {
   # impossible to add correct supressions, that means if "/usr/lib/debug"
   # is available, it should be added to
   # LD_LIBRARY_PATH
+  #
+  # But pthread is broken in libc6-dbg on Debian <= 3.1 (see Debian
+  # bug 399035, http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=399035),
+  # so don't change LD_LIBRARY_PATH on that platform.
   # --------------------------------------------------------------------------
   my $debug_libraries_path= "/usr/lib/debug";
-  if (  $opt_valgrind and -d $debug_libraries_path )
+  my $deb_version;
+  if (  $opt_valgrind and -d $debug_libraries_path and
+        (! -e '/etc/debian_version' or
+         ($deb_version= mtr_grab_file('/etc/debian_version')) == 0 or
+         $deb_version > 3.1 ) )
   {
     push(@ld_library_paths, $debug_libraries_path);
   }