diff --git a/src/common.h b/src/common.h
index 56e14d1..82d5ba1 100644
--- a/src/common.h
+++ b/src/common.h
@@ -40,7 +40,6 @@ typedef int32_t int32;
 
 #define _MAX_PATH PATH_MAX
 #define sscanf_s sscanf
-#define sprintf_s snprintf
 
 inline void strcpy_s(char* dst, size_t n, const char* src)
 {
diff --git a/src/resource.cpp b/src/resource.cpp
index 076b6cc..07fd1ad 100644
--- a/src/resource.cpp
+++ b/src/resource.cpp
@@ -19,7 +19,7 @@ SDL_RWops* open_resource(const char* name, const char* type) {
 	// On Android, read from APK assets.
 	// On other platforms, read from a file under RESOURCE_PATH.
 	char path[_MAX_PATH];
-	sprintf_s(path, _MAX_PATH, "%s%s/%s", RESOURCE_PATH, type, name);
+	snprintf(path, _MAX_PATH, "%s%s/%s", RESOURCE_PATH, type, name);
 	return SDL_RWFromFile(path, "rb");
 #endif
 }
diff --git a/src/sdlmain.cpp b/src/sdlmain.cpp
index a28ff46..69ad134 100644
--- a/src/sdlmain.cpp
+++ b/src/sdlmain.cpp
@@ -73,7 +73,7 @@ int main(int argc, char *argv[])
 	const char* title = g_nact->get_title();
 	if (title) {
 		char buf[128];
-		sprintf_s(buf, 128, "System3-sdl2 " SYSTEM3_VERSION ": %s", title);
+		snprintf(buf, 128, "System3-sdl2 " SYSTEM3_VERSION ": %s", title);
 #ifdef __EMSCRIPTEN__
 		EM_ASM_ARGS({ xsystem35.shell.setWindowTitle(UTF8ToString($0)); }, buf);
 #else
diff --git a/src/sys/ags_draw.cpp b/src/sys/ags_draw.cpp
index 3ee7900..5f356b5 100644
--- a/src/sys/ags_draw.cpp
+++ b/src/sys/ags_draw.cpp
@@ -19,12 +19,12 @@ void AGS::load_cg(int page, int transparent)
 		// あゆみちゃん物語 フルカラー実写版
 		if(strncmp(acg, "CGA000.BMP", 10) == 0) {
 			char file_name[16];
-			sprintf(file_name, "CGA%03d.BMP", page);
+			snprintf(file_name, sizeof(file_name), "CGA%03d.BMP", page);
 			load_bmp(file_name);
 			return;
 		} else if(strncmp(acg, "CGB000.BMP", 10) == 0) {
 			char file_name[16];
-			sprintf(file_name, "CGB%03d.BMP",  page);
+			snprintf(file_name, sizeof(file_name), "CGB%03d.BMP", page);
 			load_bmp(file_name);
 			return;
 		}
diff --git a/src/sys/nact_sys1.cpp b/src/sys/nact_sys1.cpp
index 43c914f..06b0a52 100644
--- a/src/sys/nact_sys1.cpp
+++ b/src/sys/nact_sys1.cpp
@@ -689,7 +689,7 @@ void NACT_Sys1::cmd_l()
 	if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_READ_BINARY | FILEIO_SAVEDATA)) {
@@ -837,7 +837,7 @@ void NACT_Sys1::cmd_q()
 	if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_WRITE_BINARY | FILEIO_SAVEDATA)) {
@@ -1045,7 +1045,7 @@ void NACT_Sys1::cmd_y()
 			case 3:
 				{
 					char buf[16];
-					sprintf(buf, "%d", param);
+					snprintf(buf, sizeof(buf), "%d", param);
 					ags->draw_text(buf);
 				}
 				break;
diff --git a/src/sys/nact_sys2.cpp b/src/sys/nact_sys2.cpp
index 649c6db..81c4d70 100644
--- a/src/sys/nact_sys2.cpp
+++ b/src/sys/nact_sys2.cpp
@@ -748,7 +748,7 @@ void NACT_Sys2::cmd_l()
 	if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_READ_BINARY | FILEIO_SAVEDATA)) {
@@ -927,7 +927,7 @@ void NACT_Sys2::cmd_q()
 	if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_WRITE_BINARY | FILEIO_SAVEDATA)) {
diff --git a/src/sys/nact_sys3.cpp b/src/sys/nact_sys3.cpp
index 7426cef..87592fc 100644
--- a/src/sys/nact_sys3.cpp
+++ b/src/sys/nact_sys3.cpp
@@ -619,7 +619,7 @@ void NACT_Sys3::cmd_l()
 	} else if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_READ_BINARY | FILEIO_SAVEDATA)) {
@@ -711,7 +711,7 @@ void NACT_Sys3::cmd_l()
 	} else if(101 <= index && index <= 126) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 101);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 101);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_READ_BINARY | FILEIO_SAVEDATA)) {
@@ -880,7 +880,7 @@ void NACT_Sys3::cmd_q()
 	} else if(1 <= index && index <= 26) {
 		// ASLEEP_A.DAT - ASLEEP_Z.DAT
 		char file_name[_MAX_PATH];
-		sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
+		snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + index - 1);
 
 		FILEIO* fio = new FILEIO();
 		if(fio->Fopen(file_name, FILEIO_WRITE_BINARY | FILEIO_SAVEDATA)) {
@@ -1344,7 +1344,7 @@ void NACT_Sys3::cmd_y()
 		case 239:
 			if(1 <= param && param <= 26) {
 				char file_name[_MAX_PATH];
-				sprintf_s(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + param - 1);
+				snprintf(file_name, _MAX_PATH, "ASLEEP_%c.DAT", 'A' + param - 1);
 
 				struct stat statbuf;
 				if (FILEIO::StatSavedata(file_name, &statbuf) != -1) {