diff --git a/README.md b/README.md
index 6ccf1e8..7c456bf 100644
--- a/README.md
+++ b/README.md
@@ -113,6 +113,10 @@ of small previews is displayed, making it easy to choose an image to open.
     N            Go [count] marked images forward
     P            Go [count] marked images backward
 
+    Ctrl-x KEY	 Execute $XDG_CONFIG_HOME/sxiv/exec/key-handler with
+                 KEY and the path of the current image as arguments.
+		 If KEY is Escape, it cancels the effect of Ctrl-x.
+
 *Thumbnail mode:*
 
     h,j,k,l      Move selection left/down/up/right [count] times
diff --git a/config.def.h b/config.def.h
index 6c03bc1..1fa8de7 100644
--- a/config.def.h
+++ b/config.def.h
@@ -77,6 +77,12 @@ static const bool RENDER_WHITE_ALPHA = false;
 #endif
 #ifdef _MAPPINGS_CONFIG
 
+/* the prefix key: when pressed, the next key combo is passed to the external
+ * key handler
+ */
+#define PREFIX_KEYMASK ControlMask
+#define PREFIX_KEYSYM XK_x
+
 /* keyboard mappings for image and thumbnail mode: */
 static const keymap_t keys[] = {
 	/* modifiers    key               function              argument */
diff --git a/exec/key-handler b/exec/key-handler
index f4de310..db1fe2f 100644
--- a/exec/key-handler
+++ b/exec/key-handler
@@ -1,9 +1,9 @@
 #!/bin/sh
 
 # Example for $XDG_CONFIG_HOME/sxiv/exec/key-handler
-# Called by sxiv(1) whenever an unbound key combo is used,
-# with the key combo as its first argument and the path of the current image
-# as its second argument.
+# Called by sxiv(1) when you press the prefix key (C-x by default) followed by
+# a key combo. The key combo is passed as its first argument and the path of
+# the current image as its second argument.
 # sxiv(1) blocks until this script terminates. It then checks if the image
 # has been modified and reloads it.
 
diff --git a/main.c b/main.c
index be91d68..5d1ef41 100644
--- a/main.c
+++ b/main.c
@@ -504,6 +504,7 @@ void run_key_handler(const char *key, unsigned int mask)
 
 void on_keypress(XKeyEvent *kev)
 {
+	static bool seen_prefix_key = false;
 	int i;
 	unsigned int sh;
 	KeySym ksym, shksym;
@@ -523,6 +524,17 @@ void on_keypress(XKeyEvent *kev)
 	if (IsModifierKey(ksym))
 		return;
 
+	if (seen_prefix_key) {
+		seen_prefix_key = false;
+		if (!(MODMASK(kev->state) == 0 && ksym == XK_Escape))
+			run_key_handler(XKeysymToString(ksym), kev->state & ~sh);
+		return;
+	} else if (MODMASK(kev->state) == PREFIX_KEYMASK && ksym == PREFIX_KEYSYM) {
+		seen_prefix_key = true;
+		prefix = 0;
+		return;
+	}
+
 	if ((ksym == XK_Escape && MODMASK(kev->state) == 0) ||
 		  (key >= '0' && key <= '9'))
 	{
@@ -545,8 +557,6 @@ void on_keypress(XKeyEvent *kev)
 			break;
 		}
 	}
-	if (i == ARRLEN(keys))
-		run_key_handler(XKeysymToString(ksym), kev->state & ~sh);
 	prefix = 0;
 }