diff --git a/input-keys.c b/input-keys.c
index a3252855..ffd2201c 100644
--- a/input-keys.c
+++ b/input-keys.c
@@ -476,7 +476,7 @@ input_key(struct screen *s, struct bufferevent *bev, key_code key)
 		input_key_write(__func__, bev, &ud.data[0], 1);
 		return (0);
 	}
-	if (justkey > 0x7f && justkey < KEYC_BASE) {
+	if (KEYC_IS_UNICODE(justkey)) {
 		if (key & KEYC_META)
 			input_key_write(__func__, bev, "\033", 1);
 		utf8_to_data(justkey, &ud);
diff --git a/key-string.c b/key-string.c
index c24a33fc..b41eaa73 100644
--- a/key-string.c
+++ b/key-string.c
@@ -238,7 +238,7 @@ key_string_lookup_string(const char *string)
 	}
 
 	/* Convert the standard control keys. */
-	if (key < KEYC_BASE &&
+	if (KEYC_IS_UNICODE(key) &&
 	    (modifiers & KEYC_CTRL) &&
 	    strchr(other, key) == NULL &&
 	    key != 9 &&
@@ -368,8 +368,8 @@ key_string_lookup_key(key_code key, int with_flags)
 		goto out;
 	}
 
-	/* Is this a UTF-8 key? */
-	if (key > 127 && key < KEYC_BASE) {
+	/* Is this a Unicode key? */
+	if (KEYC_IS_UNICODE(key)) {
 		utf8_to_data(key, &ud);
 		off = strlen(out);
 		memcpy(out + off, ud.data, ud.size);
diff --git a/status.c b/status.c
index 271e1afa..f4418500 100644
--- a/status.c
+++ b/status.c
@@ -1300,7 +1300,7 @@ process_key:
 	return (0);
 
 append_key:
-	if (key <= 0x1f || key >= KEYC_BASE)
+	if (key <= 0x1f || (key >= KEYC_BASE && key < KEYC_BASE_END))
 		return (0);
 	if (key <= 0x7f)
 		utf8_set(&tmp, key);
diff --git a/tmux.h b/tmux.h
index b0abb523..e54eb2d0 100644
--- a/tmux.h
+++ b/tmux.h
@@ -109,11 +109,16 @@ struct winlink;
 #define VISUAL_ON 1
 #define VISUAL_BOTH 2
 
-/* Special key codes. */
-#define KEYC_NONE            0x00ff000000000ULL
-#define KEYC_UNKNOWN         0x00fe000000000ULL
-#define KEYC_BASE            0x0001000000000ULL
-#define KEYC_USER            0x0002000000000ULL
+/* No key or unknown key. */
+#define KEYC_NONE            0x000ff000000000ULL
+#define KEYC_UNKNOWN         0x000fe000000000ULL
+
+/*
+ * Base for special (that is, not Unicode) keys. An enum must be at most a
+ * signed int, so these are based in the highest Unicode PUA.
+ */
+#define KEYC_BASE            0x0000000010e000ULL
+#define KEYC_USER            0x0000000010f000ULL
 
 /* Key modifier bits. */
 #define KEYC_META            0x00100000000000ULL
@@ -136,8 +141,15 @@ struct winlink;
 #define KEYC_NUSER 1000
 
 /* Is this a mouse key? */
-#define KEYC_IS_MOUSE(key) (((key) & KEYC_MASK_KEY) >= KEYC_MOUSE &&	\
-    ((key) & KEYC_MASK_KEY) < KEYC_BSPACE)
+#define KEYC_IS_MOUSE(key) \
+	(((key) & KEYC_MASK_KEY) >= KEYC_MOUSE && \
+	 ((key) & KEYC_MASK_KEY) < KEYC_BSPACE)
+
+/* Is this a Unicode key? */
+#define KEYC_IS_UNICODE(key) \
+	(((key) & KEYC_MASK_KEY) > 0x7f && \
+	 (((key) & KEYC_MASK_KEY) < KEYC_BASE || \
+	  ((key) & KEYC_MASK_KEY) >= KEYC_BASE_END))
 
 /* Multiple click timeout. */
 #define KEYC_CLICK_TIMEOUT 300
@@ -159,8 +171,8 @@ struct winlink;
 	{ #s "Border", KEYC_ ## name ## _BORDER }
 
 /*
- * A single key. This can be ASCII or Unicode or one of the keys starting at
- * KEYC_BASE.
+ * A single key. This can be ASCII or Unicode or one of the keys between
+ * KEYC_BASE and KEYC_BASE_END.
  */
 typedef unsigned long long key_code;
 
@@ -253,6 +265,9 @@ enum {
 	KEYC_KP_ENTER,
 	KEYC_KP_ZERO,
 	KEYC_KP_PERIOD,
+
+	/* End of special keys. */
+	KEYC_BASE_END
 };
 
 /* Termcap codes. */