diff --git a/acme.sh b/acme.sh
index 81a20b0b..0c8ab903 100755
--- a/acme.sh
+++ b/acme.sh
@@ -268,31 +268,31 @@ _usage() {
 __debug_bash_helper() {
   # At this point only do for --debug 3
   if [ "${DEBUG:-$DEBUG_LEVEL_NONE}" -lt "$DEBUG_LEVEL_3" ]; then
-    echo ""
     return
   fi
   # Return extra debug info when running with bash, otherwise return empty
   # string.
   if [ -z "${BASH_VERSION}" ]; then
-    echo ""
     return
   fi
   # We are a bash shell at this point, return the filename, function name, and
   # line number as a string
   _dbh_saveIFS=$IFS
   IFS=" "
-  # Must use eval or syntax error happens under dash
+  # Must use eval or syntax error happens under dash. The eval should use
+  # single quotes as older versions of busybox had a bug with double quotes and
+  # eval.
   # Use 'caller 1' as we want one level up the stack as we should be called
   # by one of the _debug* functions
-  eval "_dbh_called=($(caller 1))"
+  eval '_dbh_called=($(caller 1))'
   IFS=$_dbh_saveIFS
-  _dbh_file=${_dbh_called[2]}
+  eval '_dbh_file=${_dbh_called[2]}'
   if [ -n "${_script_home}" ]; then
     # Trim off the _script_home directory name
-    _dbh_file=${_dbh_file#$_script_home/}
+    eval '_dbh_file=${_dbh_file#$_script_home/}'
   fi
-  _dbh_function=${_dbh_called[1]}
-  _dbh_lineno=${_dbh_called[0]}
+  eval '_dbh_function=${_dbh_called[1]}'
+  eval '_dbh_lineno=${_dbh_called[0]}'
   printf "%-40s " "$_dbh_file:${_dbh_function}:${_dbh_lineno}"
 }