diff --git a/ChangeLog b/ChangeLog
index d02c235..35678de 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -10,6 +10,7 @@
 	* include/kernaux/ntoa.h: Functions "kernaux_[u|i]toa16" put default prefix
 	* include/kernaux/ntoa.h: Add octal functions "kernaux_[u|i]toa8"
 	* include/kernaux/ntoa.h: Add binary functions "kernaux_[u|i]toa2"
+	* src/ntoa.h: Protect caller from invalid state in case of future assertions
 
 2022-05-28  Alex Kotov  <kotovalexarian@gmail.com>
 
diff --git a/src/ntoa.c b/src/ntoa.c
index d00faae..d3b952d 100644
--- a/src/ntoa.c
+++ b/src/ntoa.c
@@ -11,6 +11,9 @@ char *kernaux_utoa(uint64_t value, char *buffer, int base, const char *prefix)
 {
     KERNAUX_NOTNULL_RETVAL(buffer, NULL);
 
+    // Protect caller from invalid state in case of future assertions
+    *buffer = '\0';
+
     switch (base) {
     case 'b': case 'B': base = 2;   break;
     case 'o': case 'O': base = 8;   break;