diff --git a/environ.c b/environ.c
index 5abf383c..fb1c4902 100644
--- a/environ.c
+++ b/environ.c
@@ -262,6 +262,12 @@ environ_for_session(struct session *s, int no_TERM)
 		environ_set(env, "TERM", 0, "%s", value);
 		environ_set(env, "TERM_PROGRAM", 0, "%s", "tmux");
 		environ_set(env, "TERM_PROGRAM_VERSION", 0, "%s", getversion());
+		environ_set(env, "COLORTERM", 0, "truecolor");
+	} else {
+		environ_unset(env, "TERM");
+		environ_unset(env, "TERM_PROGRAM");
+		environ_unset(env, "TERM_PROGRAM_VERSION");
+		environ_unset(env, "COLORTERM");
 	}
 
 	if (s != NULL)
diff --git a/tty-term.c b/tty-term.c
index 460b761f..b6b0dfce 100644
--- a/tty-term.c
+++ b/tty-term.c
@@ -532,6 +532,7 @@ tty_term_create(struct tty *tty, char *name, char **caps, u_int ncaps,
 	size_t					 offset, namelen;
 	char					*first;
 	int					 n;
+	struct environ_entry			*envent;
 
 	log_debug("adding term %s", name);
 
@@ -595,6 +596,17 @@ tty_term_create(struct tty *tty, char *name, char **caps, u_int ncaps,
 		a = options_array_next(a);
 	}
 
+	/* Check for COLORTERM. */
+	envent = environ_find(tty->client->environ, "COLORTERM");
+	if (envent != NULL) {
+		log_debug("%s COLORTERM=%s", tty->client->name, envent->value);
+		if (strcasecmp(envent->value, "truecolor") == 0 ||
+		    strcasecmp(envent->value, "24bit") == 0)
+			tty_add_features(feat, "RGB", ",");
+ 		else if (strstr(s, "256") != NULL)
+			tty_add_features(feat, "256", ",");
+	}
+
 	/* Apply overrides so any capabilities used for features are changed. */
 	tty_term_apply_overrides(term);