diff --git a/src/console.cpp b/src/console.cpp
index 29bab2f740..2274da64fe 100644
--- a/src/console.cpp
+++ b/src/console.cpp
@@ -137,7 +137,7 @@ void CDECL IConsolePrintF(TextColour colour_code, const char *format, ...)
 	char buf[ICON_MAX_STREAMSIZE];
 
 	va_start(va, format);
-	vsnprintf(buf, sizeof(buf), format, va);
+	vseprintf(buf, lastof(buf), format, va);
 	va_end(va);
 
 	IConsolePrint(colour_code, buf);
diff --git a/src/debug.cpp b/src/debug.cpp
index ad99dc38d8..16eecadad0 100644
--- a/src/debug.cpp
+++ b/src/debug.cpp
@@ -163,7 +163,7 @@ void CDECL debug(const char *dbg, const char *format, ...)
 
 	va_list va;
 	va_start(va, format);
-	vsnprintf(buf, lengthof(buf), format, va);
+	vseprintf(buf, lastof(buf), format, va);
 	va_end(va);
 
 	debug_print(dbg, buf);
diff --git a/src/game/game_text.cpp b/src/game/game_text.cpp
index 83dc9a6044..30e6304950 100644
--- a/src/game/game_text.cpp
+++ b/src/game/game_text.cpp
@@ -31,7 +31,7 @@ void CDECL strgen_warning(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	DEBUG(script, 0, "%s:%d: warning: %s", _file, _cur_line, buf);
 	_warnings++;
@@ -42,7 +42,7 @@ void CDECL strgen_error(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	DEBUG(script, 0, "%s:%d: error: %s", _file, _cur_line, buf);
 	_errors++;
@@ -53,7 +53,7 @@ void NORETURN CDECL strgen_fatal(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	DEBUG(script, 0, "%s:%d: FATAL: %s", _file, _cur_line, buf);
 	throw std::exception();
diff --git a/src/misc/str.hpp b/src/misc/str.hpp
index b109b4e82f..b982913fc2 100644
--- a/src/misc/str.hpp
+++ b/src/misc/str.hpp
@@ -100,7 +100,7 @@ struct CStrA : public CBlobT<char>
 		int err = 0;
 		for (;;) {
 			char *buf = MakeFreeSpace(addSize);
-			ret = vsnprintf(buf, base::GetReserve(), format, args);
+			ret = vseprintf(buf, buf + base::GetReserve() - 1, format, args);
 			if (ret >= (int)base::GetReserve()) {
 				/* Greater return than given count means needed buffer size. */
 				addSize = ret + 1;
diff --git a/src/network/network_chat_gui.cpp b/src/network/network_chat_gui.cpp
index f8a0867f34..b1a5dcb55d 100644
--- a/src/network/network_chat_gui.cpp
+++ b/src/network/network_chat_gui.cpp
@@ -86,7 +86,7 @@ void CDECL NetworkAddChatMessage(TextColour colour, uint duration, const char *m
 	va_list va;
 
 	va_start(va, message);
-	vsnprintf(buf, lengthof(buf), message, va);
+	vseprintf(buf, lastof(buf), message, va);
 	va_end(va);
 
 	Utf8TrimString(buf, DRAW_STRING_BUFFER);
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 90fd24bf14..079c121621 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -377,7 +377,7 @@ void CDECL grfmsg(int severity, const char *str, ...)
 	va_list va;
 
 	va_start(va, str);
-	vsnprintf(buf, sizeof(buf), str, va);
+	vseprintf(buf, lastof(buf), str, va);
 	va_end(va);
 
 	DEBUG(grf, severity, "[%s:%d] %s", _cur.grfconfig->filename, _cur.nfo_line, buf);
diff --git a/src/newgrf_debug_gui.cpp b/src/newgrf_debug_gui.cpp
index d3b5ddd164..6d5312514c 100644
--- a/src/newgrf_debug_gui.cpp
+++ b/src/newgrf_debug_gui.cpp
@@ -400,7 +400,7 @@ struct NewGRFInspectWindow : Window {
 
 		va_list va;
 		va_start(va, format);
-		vsnprintf(buf, lengthof(buf), format, va);
+		vseprintf(buf, lastof(buf), format, va);
 		va_end(va);
 
 		offset -= this->vscroll->GetPosition();
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 4dcd49fbfc..57e32489de 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -93,7 +93,7 @@ void CDECL usererror(const char *s, ...)
 	char buf[512];
 
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 
 	ShowOSErrorBox(buf, false);
@@ -113,7 +113,7 @@ void CDECL error(const char *s, ...)
 	char buf[512];
 
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 
 	ShowOSErrorBox(buf, true);
@@ -132,7 +132,7 @@ void CDECL ShowInfoF(const char *str, ...)
 	va_list va;
 	char buf[1024];
 	va_start(va, str);
-	vsnprintf(buf, lengthof(buf), str, va);
+	vseprintf(buf, lastof(buf), str, va);
 	va_end(va);
 	ShowInfo(buf);
 }
diff --git a/src/script/squirrel.cpp b/src/script/squirrel.cpp
index 9ead866e7f..99e5ae1c09 100644
--- a/src/script/squirrel.cpp
+++ b/src/script/squirrel.cpp
@@ -21,9 +21,10 @@
 
 /* Due to the different characters for Squirrel, the scsnprintf might be a simple
  * snprint which triggers the safeguard. But it isn't always a simple snprintf.
- * Likewise for scstrcat. */
+ * Likewise for scvsnprintf and scstrcat. */
 #include "../safeguards.h"
 #undef snprintf
+#undef vsnprintf
 #undef strcat
 
 void Squirrel::CompileError(HSQUIRRELVM vm, const SQChar *desc, const SQChar *source, SQInteger line, SQInteger column)
diff --git a/src/settingsgen/settingsgen.cpp b/src/settingsgen/settingsgen.cpp
index 9f8cc10501..dd92e2627b 100644
--- a/src/settingsgen/settingsgen.cpp
+++ b/src/settingsgen/settingsgen.cpp
@@ -42,7 +42,7 @@ void NORETURN CDECL error(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	fprintf(stderr, "FATAL: %s\n", buf);
 	exit(1);
diff --git a/src/strgen/strgen.cpp b/src/strgen/strgen.cpp
index 2fb89f0885..4cd2454f4e 100644
--- a/src/strgen/strgen.cpp
+++ b/src/strgen/strgen.cpp
@@ -53,7 +53,7 @@ void CDECL strgen_warning(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	fprintf(stderr, LINE_NUM_FMT("warning"), _file, _cur_line, buf);
 	_warnings++;
@@ -64,7 +64,7 @@ void CDECL strgen_error(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	fprintf(stderr, LINE_NUM_FMT("error"), _file, _cur_line, buf);
 	_errors++;
@@ -75,7 +75,7 @@ void NORETURN CDECL strgen_fatal(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	fprintf(stderr, LINE_NUM_FMT("FATAL"), _file, _cur_line, buf);
 #ifdef _MSC_VER
@@ -89,7 +89,7 @@ void NORETURN CDECL error(const char *s, ...)
 	char buf[1024];
 	va_list va;
 	va_start(va, s);
-	vsnprintf(buf, lengthof(buf), s, va);
+	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 	fprintf(stderr, LINE_NUM_FMT("FATAL"), _file, _cur_line, buf);
 #ifdef _MSC_VER
diff --git a/src/string.cpp b/src/string.cpp
index 8a95d7b6fe..63288e4316 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -32,7 +32,10 @@
 #include "gfx_func.h"
 #endif /* WITH_ICU */
 
+/* The function vsnprintf is used internally to perform the required formatting
+ * tasks. As such this one must be allowed, and makes sure it's terminated. */
 #include "safeguards.h"
+#undef vsnprintf
 
 /**
  * Safer implementation of vsnprintf; same as vsnprintf except:
@@ -44,7 +47,7 @@
  * @param ap     the list of arguments for the format
  * @return the number of added characters
  */
-static int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap)
+int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap)
 {
 	ptrdiff_t diff = last - str;
 	if (diff < 0) return 0;
diff --git a/src/string_func.h b/src/string_func.h
index 8354d67cde..474340a69f 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -34,6 +34,7 @@ char *strecpy(char *dst, const char *src, const char *last);
 char *stredup(const char *src, const char *last = NULL);
 
 int CDECL seprintf(char *str, const char *last, const char *format, ...) WARN_FORMAT(3, 4);
+int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap);
 
 char *CDECL str_fmt(const char *str, ...) WARN_FORMAT(1, 2);
 
diff --git a/src/textbuf.cpp b/src/textbuf.cpp
index c11e3c1bf1..116d60ba87 100644
--- a/src/textbuf.cpp
+++ b/src/textbuf.cpp
@@ -419,7 +419,7 @@ void Textbuf::Print(const char *format, ...)
 {
 	va_list va;
 	va_start(va, format);
-	vsnprintf(this->buf, this->max_bytes, format, va);
+	vseprintf(this->buf, &this->buf[this->max_bytes - 1], format, va);
 	va_end(va);
 	this->UpdateSize();
 }