diff --git a/completions/crontab b/completions/crontab
index 2cad8521..1e21f824 100644
--- a/completions/crontab
+++ b/completions/crontab
@@ -14,35 +14,31 @@ _crontab()
             ;;
     esac
 
-    local i opts=" -u -l -r -e" # leading space at start is significant...
-    [[ $OSTYPE == *linux* ]] && opts+=" -i"
-    [ -e /etc/selinux ] && opts+=" -s"
+    local -A opts=( [-u]= [-l]= [-r]= [-e]= )
+    [[ $OSTYPE == *linux* ]] && opts[-i]=
+    [ -e /etc/selinux ] && opts[-s]=
+
+    local i
     for (( i=0; i < ${#words[@]}-1; i++ )); do
+        [[ ${words[i]} ]] && unset opts[${words[i]}]
         case "${words[i]}" in
             -l)
-                opts=${opts// -l -r -e/}
-                opts=${opts// -i/}
-                opts=${opts// -s/}
+                unset opts[-r] opts[-e] opts[-i] opts[-s]
                 ;;
             -e)
-                opts=${opts// -l -r -e/}
-                opts=${opts// -i/}
+                unset opts[-l] opts[-r] opts[-i]
                 ;;
             -r)
-                opts=${opts// -l -r -e/}
+                unset opts[-l] opts[-e]
                 ;;
             -u)
-                opts=${opts// -u/}
-                opts=${opts// -i/}
-                ;;
-            -i|-s)
-                opts=${opts// ${words[i]}/}
+                unset opts[-i]
                 ;;
         esac
     done
 
     if [[ "$cur" == -* ]]; then
-        COMPREPLY=( $( compgen -W '$opts' -- "$cur" ) )
+        COMPREPLY=( $( compgen -W '${!opts[@]}' -- "$cur" ) )
         return 0
     fi
 
diff --git a/completions/findutils b/completions/findutils
index 23260e47..cd1c4404 100644
--- a/completions/findutils
+++ b/completions/findutils
@@ -91,27 +91,23 @@ _find()
         -delete -exec -execdir -fls -fprint -fprint0 -fprintf -ls -ok -okdir \
         -print -print0 -printf -prune -quit' -- "$cur" ) )
 
-    # this removes any options from the list of completions that have
-    # already been specified somewhere on the command line, as long as
-    # these options can only be used once (in a word, "options", in
-    # opposition to "tests" and "actions", as in the find(1) manpage).
-    local onlyonce
-    onlyonce=' -daystart -depth -follow -help -ignore_readdir_race -maxdepth \
-       -mindepth -mount -noignore_readdir_race -noleaf -nowarn -regextype \
-       -version -warn -xdev '
-    COMPREPLY=( $( \
-           (while read -d ' ' i; do
-            [[ -z "$i" || "${onlyonce/ ${i%% *} / }" == "$onlyonce" ]] &&
-            continue
-            # flatten array with spaces on either side,
-            # otherwise we cannot grep on word boundaries of
-            # first and last word
-            COMPREPLY=" ${COMPREPLY[@]} "
-            # remove word from list of completions
-            COMPREPLY=( ${COMPREPLY/ ${i%% *} / } )
+    if [[ ${#COMPREPLY[@]} -ne 0 ]]; then
+        # this removes any options from the list of completions that have
+        # already been specified somewhere on the command line, as long as
+        # these options can only be used once (in a word, "options", in
+        # opposition to "tests" and "actions", as in the find(1) manpage).
+        local -A onlyonce=( [-daystart]=1 [-depth]=1 [-follow]=1 [-help]=1
+            [-ignore_readdir_race]=1 [-maxdepth]=1 [-mindepth]=1 [-mount]=1
+            [-noignore_readdir_race]=1 [-noleaf]=1 [-nowarn]=1 [-regextype]=1
+            [-version]=1 [-warn]=1 [-xdev]=1 )
+        local j
+        for i in "${words[@]}"; do
+            [[ $i && ${onlyonce[$i]} ]] || continue
+            for j in ${!COMPREPLY[@]}; do
+                [[ ${COMPREPLY[j]} == $i ]] && unset COMPREPLY[j]
             done
-            printf '%s ' "${COMPREPLY[@]}") <<<"${words[@]}"
-          ) )
+        done
+    fi
 
     _filedir