diff --git a/src/dialogs/menu.c b/src/dialogs/menu.c
index 0707b9807..172965ca2 100644
--- a/src/dialogs/menu.c
+++ b/src/dialogs/menu.c
@@ -759,7 +759,7 @@ do_pass_uri_to_command(struct terminal *term, void *command_, void *xxx)
 {
 	unsigned char *command = command_;
 
-	exec_on_terminal(term, command, "", 0);
+	exec_on_terminal(term, command, "", TERM_EXEC_BG);
 	mem_free(command);
 }
 
diff --git a/src/osdep/newwin.c b/src/osdep/newwin.c
index 25e4fe1ad..8c92300d3 100644
--- a/src/osdep/newwin.c
+++ b/src/osdep/newwin.c
@@ -90,6 +90,6 @@ open_new_window(struct terminal *term, unsigned char *exe_name,
 			     (unsigned char *) NULL);
 	if (!command) return;
 
-	exec_on_terminal(term, command, "", 2);
+	exec_on_terminal(term, command, "", TERM_EXEC_NEWWIN);
 	mem_free(command);
 }
diff --git a/src/protocol/user.c b/src/protocol/user.c
index 3a92ead71..e0b3f6288 100644
--- a/src/protocol/user.c
+++ b/src/protocol/user.c
@@ -300,7 +300,7 @@ user_protocol_handler(struct session *ses, struct uri *uri)
 	if (prog) {
 		unsigned char *delete = empty_string_or_(filename);
 
-		exec_on_terminal(ses->tab->term, prog, delete, 1);
+		exec_on_terminal(ses->tab->term, prog, delete, TERM_EXEC_FG);
 		mem_free(prog);
 
 	} else if (filename) {
diff --git a/src/scripting/lua/core.c b/src/scripting/lua/core.c
index bd1b8df0c..8aec3a91a 100644
--- a/src/scripting/lua/core.c
+++ b/src/scripting/lua/core.c
@@ -231,7 +231,8 @@ static int
 l_execute(LS)
 {
 	if (lua_isstring(S, 1)) {
-		exec_on_terminal(lua_ses->tab->term, (unsigned char *) lua_tostring(S, 1), "", 0);
+		exec_on_terminal(lua_ses->tab->term, (unsigned char *) lua_tostring(S, 1), "",
+				 TERM_EXEC_BG);
 		lua_pushnumber(S, 0);
 		return 1;
 	}
@@ -795,7 +796,7 @@ handle_ret_run(struct session *ses)
 	unsigned char *cmd = (unsigned char *) lua_tostring(L, -1);
 
 	if (cmd) {
-		exec_on_terminal(ses->tab->term, cmd, "", 1);
+		exec_on_terminal(ses->tab->term, cmd, "", TERM_EXEC_FG);
 		return;
 	}
 
diff --git a/src/scripting/smjs/elinks_object.c b/src/scripting/smjs/elinks_object.c
index e017723b9..55d7a2970 100644
--- a/src/scripting/smjs/elinks_object.c
+++ b/src/scripting/smjs/elinks_object.c
@@ -103,7 +103,7 @@ elinks_execute(JSContext *ctx, JSObject *obj, uintN argc, jsval *argv, jsval *rv
 	if (!*string)
 		return JS_TRUE;
 
-	exec_on_terminal(smjs_ses->tab->term, string, "", 0);
+	exec_on_terminal(smjs_ses->tab->term, string, "", TERM_EXEC_BG);
 	undef_to_jsval(ctx, rval);
 
 	return JS_TRUE;
diff --git a/src/session/download.c b/src/session/download.c
index 3f3412129..376a29446 100644
--- a/src/session/download.c
+++ b/src/session/download.c
@@ -376,7 +376,7 @@ download_data_store(struct download *download, struct file_download *file_downlo
 		} else {
 			exec_on_terminal(term, file_download->external_handler,
 				 file_download->file,
-				 !!file_download->block);
+				 file_download->block ? TERM_EXEC_FG : TERM_EXEC_BG);
 			file_download->delete = 0;
 			abort_download_and_beep(file_download, term);
 		}
@@ -1100,7 +1100,8 @@ tp_open(struct type_query *type_query)
 				read_from_popen(type_query->ses, handler, NULL);
 			else
 				exec_on_terminal(type_query->ses->tab->term,
-					 handler, "", !!type_query->block);
+					 handler, "",
+					 type_query->block ? TERM_EXEC_FG : TERM_EXEC_BG);
 			mem_free(handler);
 		}
 
diff --git a/src/terminal/kbd.c b/src/terminal/kbd.c
index 16be876b0..9a7f54406 100644
--- a/src/terminal/kbd.c
+++ b/src/terminal/kbd.c
@@ -510,7 +510,7 @@ in_sock(struct itrm *itrm)
 	struct string path;
 	struct string delete;
 	char ch;
-	int fg;
+	int fg; /* enum term_exec */
 	ssize_t bytes_read, i, p;
 	unsigned char buf[ITRM_OUT_QUEUE_SIZE];
 
@@ -575,7 +575,7 @@ has_nul_byte:
 		unsigned char *param;
 		int path_len, del_len, param_len;
 
-		if (is_blocked() && fg) {
+		if (is_blocked() && fg != TERM_EXEC_BG) {
 			if (*delete.source) unlink(delete.source);
 			goto nasty_thing;
 		}
@@ -591,20 +591,20 @@ has_nul_byte:
 		memcpy(param + 1, path.source, path_len + 1);
 		memcpy(param + 1 + path_len + 1, delete.source, del_len + 1);
 
-		if (fg == 1) block_itrm();
+		if (fg == TERM_EXEC_FG) block_itrm();
 
 		blockh = start_thread((void (*)(void *, int)) exec_thread,
 				      param, param_len);
 		mem_free(param);
 
 		if (blockh == -1) {
-			if (fg == 1)
+			if (fg == TERM_EXEC_FG)
 				unblock_itrm();
 
 			goto nasty_thing;
 		}
 
-		if (fg == 1) {
+		if (fg == TERM_EXEC_FG) {
 			set_handlers(blockh, (select_handler_T) unblock_itrm_x,
 				     NULL, (select_handler_T) unblock_itrm_x,
 				     (void *) (long) blockh);
diff --git a/src/terminal/terminal.c b/src/terminal/terminal.c
index befaa0a1d..00a2854c4 100644
--- a/src/terminal/terminal.c
+++ b/src/terminal/terminal.c
@@ -179,7 +179,7 @@ exec_thread(unsigned char *path, int p)
 	int plen = strlen(path + 1) + 2;
 
 #if defined(HAVE_SETPGID) && !defined(CONFIG_OS_BEOS) && !defined(HAVE_BEGINTHREAD)
-	if (path[0] == 2) setpgid(0, 0);
+	if (path[0] == TERM_EXEC_NEWWIN) setpgid(0, 0);
 #endif
 	exe(path + 1);
 	if (path[plen]) unlink(path + plen);
@@ -210,7 +210,7 @@ static void
 exec_on_master_terminal(struct terminal *term,
 			unsigned char *path, int plen,
 		 	unsigned char *delete, int dlen,
-			int fg)
+			enum term_exec fg)
 {
 	int blockh;
 	int param_size = plen + dlen + 2 /* 2 null char */ + 1 /* fg */;
@@ -222,17 +222,17 @@ exec_on_master_terminal(struct terminal *term,
 	memcpy(param + 1, path, plen + 1);
 	memcpy(param + 1 + plen + 1, delete, dlen + 1);
 
-	if (fg == 1) block_itrm();
+	if (fg == TERM_EXEC_FG) block_itrm();
 
 	blockh = start_thread((void (*)(void *, int)) exec_thread,
 			      param, param_size);
 	fmem_free(param);
 	if (blockh == -1) {
-		if (fg == 1) unblock_itrm();
+		if (fg == TERM_EXEC_FG) unblock_itrm();
 		return;
 	}
 
-	if (fg == 1) {
+	if (fg == TERM_EXEC_FG) {
 		term->blocked = blockh;
 		set_handlers(blockh,
 			     (select_handler_T) unblock_terminal,
@@ -253,7 +253,7 @@ static void
 exec_on_slave_terminal( struct terminal *term,
 		 	unsigned char *path, int plen,
 		 	unsigned char *delete, int dlen,
-			int fg)
+			enum term_exec fg)
 {
 	int data_size = plen + dlen + 1 /* 0 */ + 1 /* fg */ + 2 /* 2 null char */;
 	unsigned char *data = fmem_alloc(data_size);
@@ -270,7 +270,7 @@ exec_on_slave_terminal( struct terminal *term,
 
 void
 exec_on_terminal(struct terminal *term, unsigned char *path,
-		 unsigned char *delete, int fg)
+		 unsigned char *delete, enum term_exec fg)
 {
 	if (path) {
 		if (!*path) return;
@@ -279,7 +279,7 @@ exec_on_terminal(struct terminal *term, unsigned char *path,
 	}
 
 #ifdef NO_FG_EXEC
-	fg = 0;
+	fg = TERM_EXEC_BG;
 #endif
 
 	if (term->master) {
@@ -288,7 +288,7 @@ exec_on_terminal(struct terminal *term, unsigned char *path,
 			return;
 		}
 
-		if (fg && is_blocked()) {
+		if (fg != TERM_EXEC_BG && is_blocked()) {
 			unlink(delete);
 			return;
 		}
@@ -314,7 +314,7 @@ exec_shell(struct terminal *term)
 
 	sh = get_shell();
 	if (sh && *sh)
-		exec_on_terminal(term, sh, "", 1);
+		exec_on_terminal(term, sh, "", TERM_EXEC_FG);
 }
 
 
@@ -328,7 +328,7 @@ do_terminal_function(struct terminal *term, unsigned char code,
 	if (!x_data) return;
 	x_data[0] = code;
 	memcpy(x_data + 1, data, data_len + 1);
-	exec_on_terminal(term, NULL, x_data, 0);
+	exec_on_terminal(term, NULL, x_data, TERM_EXEC_BG);
 	fmem_free(x_data);
 }
 
diff --git a/src/terminal/terminal.h b/src/terminal/terminal.h
index d95da99a2..f661e02ae 100644
--- a/src/terminal/terminal.h
+++ b/src/terminal/terminal.h
@@ -175,10 +175,28 @@ void destroy_all_terminals(void);
 void exec_thread(unsigned char *, int);
 void close_handle(void *);
 
+/* Operations that can be requested with do_terminal_function().
+ * The interlink protocol passes these values as one byte in a
+ * null-terminated string, so zero cannot be used.  */
 #define TERM_FN_TITLE	1
 #define TERM_FN_RESIZE	2
 
-void exec_on_terminal(struct terminal *, unsigned char *, unsigned char *, int);
+/* How to execute a program in a terminal.  These values are used in
+ * the interlink protocol and must fit in one byte.  */
+enum term_exec {
+	/* Execute in the background.  ELinks keeps using the terminal
+	 * and the program should not use it.  */
+	TERM_EXEC_BG = 0,
+
+	/* Execute in the foreground.  The program may use the terminal.
+	 * ELinks will redraw when the program exits.  */
+	TERM_EXEC_FG = 1,
+
+	/* Execute in the background and in a new process group.  */
+	TERM_EXEC_NEWWIN = 2
+};
+
+void exec_on_terminal(struct terminal *, unsigned char *, unsigned char *, enum term_exec);
 void exec_shell(struct terminal *term);
 
 void set_terminal_title(struct terminal *, unsigned char *);
diff --git a/src/viewer/text/textarea.c b/src/viewer/text/textarea.c
index a6b739ff7..dfb446051 100644
--- a/src/viewer/text/textarea.c
+++ b/src/viewer/text/textarea.c
@@ -625,7 +625,7 @@ textarea_edit(int op, struct terminal *term_, struct form_state *fs_,
 		}
 		if (term_) term = term_;
 
-		exec_on_terminal(term, ex, "", 1);
+		exec_on_terminal(term, ex, "", TERM_EXEC_FG);
 		mem_free(ex);
 
 		textarea_editor = 1;