diff --git a/git-compat-util.h b/git-compat-util.h
index bd04564a69..4575b3890b 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1064,6 +1064,15 @@ static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
 #define HAVE_VARIADIC_MACROS 1
 #endif
 
+#ifdef HAVE_VARIADIC_MACROS
+__attribute__((format (printf, 3, 4))) NORETURN
+void BUG_fl(const char *file, int line, const char *fmt, ...);
+#define BUG(...) BUG_fl(__FILE__, __LINE__, __VA_ARGS__)
+#else
+__attribute__((format (printf, 1, 2))) NORETURN
+void BUG(const char *fmt, ...);
+#endif
+
 /*
  * Preserves errno, prints a message, but gives no warning for ENOENT.
  * Returns 0 on success, which includes trying to unlink an object that does
diff --git a/usage.c b/usage.c
index ad6d2910fb..7e6cb20280 100644
--- a/usage.c
+++ b/usage.c
@@ -201,3 +201,35 @@ void warning(const char *warn, ...)
 	warn_routine(warn, params);
 	va_end(params);
 }
+
+static NORETURN void BUG_vfl(const char *file, int line, const char *fmt, va_list params)
+{
+	char prefix[256];
+
+	/* truncation via snprintf is OK here */
+	if (file)
+		snprintf(prefix, sizeof(prefix), "BUG: %s:%d: ", file, line);
+	else
+		snprintf(prefix, sizeof(prefix), "BUG: ");
+
+	vreportf(prefix, fmt, params);
+	abort();
+}
+
+#ifdef HAVE_VARIADIC_MACROS
+void BUG_fl(const char *file, int line, const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	BUG_vfl(file, line, fmt, ap);
+	va_end(ap);
+}
+#else
+void BUG(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	BUG_vfl(NULL, 0, fmt, ap);
+	va_end(ap);
+}
+#endif