diff --git a/src/instructions.c b/src/instructions.c
index 98fa476..f5e7f03 100644
--- a/src/instructions.c
+++ b/src/instructions.c
@@ -47,7 +47,7 @@ const struct syscall syscalls[NR_SYSCALLS] = {
 	SYS  ( SYS_RESUME_SAVE,          ResumeSave ),
 	SYS  ( SYS_RESUME_LOAD,          ResumeLoad ),
 	SYS  ( SYS_EXISTS_FILE,          ExistsFile ),
-	TODO ( SYS_OPEN_WEB,             OpenWeb ),
+	SYS  ( SYS_OPEN_WEB,             OpenWeb ),
 	SYS  ( SYS_GET_SAVE_FOLDER_NAME, GetSaveFolderName ),
 	SYS  ( SYS_GET_TIME,             GetTime ),
 	TODO ( SYS_GET_GAME_NAME,        GetGameName ),
diff --git a/src/system4.c b/src/system4.c
index 38f6f65..046f8b6 100644
--- a/src/system4.c
+++ b/src/system4.c
@@ -20,6 +20,8 @@
 #include <libgen.h>
 #include <dirent.h>
 #include <ctype.h>
+#include <signal.h>
+#include <sys/wait.h>
 #include "debugger.h"
 #include "file.h"
 #include "ini.h"
@@ -195,6 +197,11 @@ static void config_init(void)
 	mkdir_p(new_save_dir);
 }
 
+void cleanup(int signal)
+{
+	while (waitpid((pid_t)-1, 0, WNOHANG) > 0);
+}
+
 int main(int argc, char *argv[])
 {
 	initialize_instructions();
@@ -226,6 +233,8 @@ int main(int argc, char *argv[])
 		ERROR("Not an AIN/INI file: %s", &argv[1][len - 4]);
 	}
 
+	signal(SIGCHLD, cleanup);
+
 	config_init();
 
 	if (!(ain = ain_open(ainfile, &err))) {
diff --git a/src/vm.c b/src/vm.c
index ee2fe93..e66055e 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -20,6 +20,8 @@
 #include <string.h>
 #include <math.h>
 #include <time.h>
+#include <errno.h>
+#include <spawn.h>
 #include <SDL.h> // for system.MsgBox
 
 #include "debugger.h"
@@ -35,6 +37,8 @@
 #include "vm/heap.h"
 #include "vm/page.h"
 
+extern char **environ;
+
 static inline int32_t lint_clamp(int64_t n)
 {
 	if (n < 0)
@@ -397,6 +401,22 @@ static void system_call(enum syscall_code code)
 		free(path);
 		break;
 	}
+	case SYS_OPEN_WEB: {
+		struct string *url = stack_peek_string(0);
+		char *browser = getenv("BROWSER");
+		if (!browser || !*browser) {
+			WARNING("$BROWSER not set, assuming Firefox");
+			browser = "firefox";
+		}
+		int err;
+		pid_t child;
+		char *argv[] = { browser, url->text, NULL };
+		if ((err = posix_spawnp(&child, browser, NULL, NULL, argv, environ))) {
+			WARNING("posix_spawn failed: %s", strerror(err));
+		}
+		heap_unref(stack_pop().i);
+		break;
+	};
 	case SYS_GET_SAVE_FOLDER_NAME: {// system.GetSaveFolderName(void)
 		if (config.save_dir) {
 			char *sjis = utf2sjis(config.save_dir, strlen(config.save_dir));