diff --git a/include/import/ist.h b/include/import/ist.h
index daf23d5..a19e228 100644
--- a/include/import/ist.h
+++ b/include/import/ist.h
@@ -425,7 +425,7 @@
 /* appends <src> after <dst>. The caller must ensure that the underlying buffer
  * is large enough to fit the character.
  */
-static inline struct ist istappend(struct ist dst, const char src)
+static inline struct ist __istappend(struct ist dst, const char src)
 {
 	dst.ptr[dst.len++] = src;