diff --git a/src/console.c b/src/console.c
index 3826b44ad..1c1893faa 100644
--- a/src/console.c
+++ b/src/console.c
@@ -1281,7 +1281,7 @@ void CONS_Alert(alerttype_t level, const char *fmt, ...)
 		txt = malloc(8192);
 
 	va_start(argptr, fmt);
-	vsprintf(txt, fmt, argptr);
+	vsnprintf(txt, 8192, fmt, argptr);
 	va_end(argptr);
 
 	switch (level)
@@ -1317,7 +1317,7 @@ void CONS_Debug(UINT32 debugflags, const char *fmt, ...)
 		txt = malloc(8192);
 
 	va_start(argptr, fmt);
-	vsprintf(txt, fmt, argptr);
+	vsnprintf(txt, 8192, fmt, argptr);
 	va_end(argptr);
 
 	// Again I am lazy, oh well
diff --git a/src/sdl/i_system.cpp b/src/sdl/i_system.cpp
index e34681af6..eef9d3f5d 100644
--- a/src/sdl/i_system.cpp
+++ b/src/sdl/i_system.cpp
@@ -2027,7 +2027,7 @@ void I_Error(const char *error, ...)
 		if (errorcount > 20)
 		{
 			va_start(argptr, error);
-			vsprintf(buffer, error, argptr);
+			vsnprintf(buffer, 8192, error, argptr);
 			va_end(argptr);
 			// Implement message box with SDL_ShowSimpleMessageBox,
 			// which should fail gracefully if it can't put a message box up
@@ -2052,7 +2052,7 @@ void I_Error(const char *error, ...)
 
 	// Display error message in the console before we start shutting it down
 	va_start(argptr, error);
-	vsprintf(buffer, error, argptr);
+	vsnprintf(buffer, 8192, error, argptr);
 	va_end(argptr);
 	I_OutputMsg("\nI_Error(): %s\n", buffer);
 	// ---
diff --git a/src/win32/win_dbg.c b/src/win32/win_dbg.c
index 9a03e9247..f37ea32c8 100644
--- a/src/win32/win_dbg.c
+++ b/src/win32/win_dbg.c
@@ -181,7 +181,7 @@ static VOID FPrintf(HANDLE fileHandle, LPCSTR lpFmt, ...)
 	DWORD   bytesWritten;
 
 	va_start(arglist, lpFmt);
-	vsprintf(str, lpFmt, arglist);
+	vsnprintf(str, 1999, lpFmt, arglist);
 	va_end(arglist);
 
 	WriteFile(fileHandle, str, (DWORD)strlen(str), &bytesWritten, NULL);