diff --git a/README.md b/README.md
index 360eb74..b175aee 100644
--- a/README.md
+++ b/README.md
@@ -22,8 +22,8 @@ there, but it basically works like this:
 ## clipmenud
 
 1. `clipmenud` polls the clipboard every 0.5 seconds (or another interval as
-   configured with the `CLIPMENUD_SLEEP` environment variable). Unfortunately
-   there's no interface to subscribe for changes in X11, so we must poll.
+   configured with the `CM_SLEEP` environment variable). Unfortunately there's
+   no interface to subscribe for changes in X11, so we must poll.
 2. If `clipmenud` detects changes to the clipboard contents, it writes them out
    to the cache directory.
 
diff --git a/clipmenu b/clipmenu
index 5094c46..203bfe3 100755
--- a/clipmenu
+++ b/clipmenu
@@ -7,7 +7,7 @@ shopt -s nullglob
 cache_dir=/tmp/clipmenu.$major_version.$USER
 cache_file=$cache_dir/line_cache
 
-: "${CM_LAUNCHER:-dmenu}"
+: "${CM_LAUNCHER=dmenu}"
 
 # It's okay to hardcode `-l 8` here as a sensible default without checking
 # whether `-l` is also in "$@", because the way that dmenu works allows a later
diff --git a/clipmenud b/clipmenud
index 782f42d..ad35888 100755
--- a/clipmenud
+++ b/clipmenud
@@ -6,6 +6,10 @@ cache_file=$cache_dir/line_cache
 lock_file=$cache_dir/lock
 lock_timeout=2
 
+: "${CM_ONESHOT=0}"
+: "${CM_OWN_CLIPBOARD=1}"
+: "${CM_DEBUG=0}"
+
 _xsel() {
     timeout 1 xsel --logfile /dev/stderr "$@"
 }
@@ -42,7 +46,7 @@ get_first_line() {
 }
 
 debug() {
-    if (( DEBUG )); then
+    if (( CM_DEBUG )); then
         printf '%s\n' "$@" >&2
     fi
 }
@@ -56,9 +60,9 @@ declare -A last_filename
 
 exec {lock_fd}> "$lock_file"
 
-while sleep "${CLIPMENUD_SLEEP:-0.5}"; do
+while sleep "${CM_SLEEP:-0.5}"; do
     if ! flock -x -w "$lock_timeout" "$lock_fd"; then
-        if (( ONESHOT )); then
+        if (( CM_ONESHOT )); then
             printf 'ERROR: %s\n' 'Timed out waiting for lock' >&2
             exit 1
         else
@@ -114,7 +118,7 @@ while sleep "${CLIPMENUD_SLEEP:-0.5}"; do
         debug "Writing $first_line to $cache_file"
         printf '%s\n' "$first_line" >> "$cache_file"
 
-        if ! (( NO_OWN_CLIPBOARD )) && [[ $selection != primary ]]; then
+        if (( CM_OWN_CLIPBOARD )) && [[ $selection != primary ]]; then
             # Take ownership of the clipboard, in case the original application
             # is unable to serve the clipboard request (due to being suspended,
             # etc).
@@ -132,7 +136,7 @@ while sleep "${CLIPMENUD_SLEEP:-0.5}"; do
 
     flock -u "$lock_fd"
 
-    if (( ONESHOT )); then
+    if (( CM_ONESHOT )); then
         debug 'Oneshot mode enabled, exiting'
         break
     fi