diff --git a/sys/include/fmt.h b/sys/include/fmt.h
index 8e89906ef8..816791cf92 100644
--- a/sys/include/fmt.h
+++ b/sys/include/fmt.h
@@ -475,6 +475,15 @@ void print_u64_hex(uint64_t val);
  */
 void print_u64_dec(uint64_t val);
 
+/**
+ * @brief Print int64 value as decimal to stdout
+ *
+ * @note This uses fmt_s64_dec(), which uses ~400b of code.
+ *
+ * @param[in]   val  Value to print
+ */
+void print_s64_dec(uint64_t val);
+
 /**
  * @brief Print float value
  *