diff --git a/cf2.md b/cf2.md
index e8b7e8e..a71a0b8 100644
--- a/cf2.md
+++ b/cf2.md
@@ -94,6 +94,9 @@ PIN_DISPLAY_MOSI = PIN_MOSI
 # custom configuration keys
 _679732427 = 123
 _815320287 = 0x80192
+
+# remove an existing config entry
+PIN_BTN_MENU2 = null
 ```
 
 The keys are either key names, or underscore followed by a decimal number.
@@ -109,6 +112,10 @@ The way pin numbers are parsed depends on the `PINS_PORT_SIZE`:
 Certain keys (like `PINS_PORT_SIZE`) have a number of pre-defined values,
 which can be used instead of integers.
 
+Because you're usually use this syntax to patch an existing configuration,
+you sometimes may want to remove an entry that's already there.
+To do that, use `null` as the value of the key.
+
 For list of keys and predefined values, see `configkeys.h` which can be downloaded
 from the patcher website.
 
diff --git a/patcher/patcher.js b/patcher/patcher.js
index 1c12ee0..041a6fc 100644
--- a/patcher/patcher.js
+++ b/patcher/patcher.js
@@ -654,6 +654,16 @@ function patchConfig(buf, cfg) {
             }
         })
 
+    let changes = ""
+    forAll((kn, k, v) => {
+        v = v.toUpperCase()
+        if (v == "NULL" || v == "UNDEFINED") {
+            let old = lookupCfg(cfgdata, k)
+            changes += "remove " + showKV(k, old, portSize0) + "\n"
+            delete cfgMap[k]
+        }
+    })
+
     forAll((kn, k, v) => {
         if (isNaN(parseInt(v)))
             err("Value not understood: " + v)
@@ -667,7 +677,6 @@ function patchConfig(buf, cfg) {
         patch.push(parseInt(cfgMap[k]))
     }
 
-    let changes = ""
     for (let i = 0; i < patch.length; i += 2) {
         let k = patch[i]
         let v = patch[i + 1]