diff --git a/src/fallback.cpp b/src/fallback.cpp
index a9ad1e1fc..8a3a467ba 100644
--- a/src/fallback.cpp
+++ b/src/fallback.cpp
@@ -9,6 +9,7 @@
 #include <errno.h>   // IWYU pragma: keep
 #include <fcntl.h>   // IWYU pragma: keep
 #include <limits.h>  // IWYU pragma: keep
+#include <unistd.h>  // IWYU pragma: keep
 #include <wctype.h>
 
 #include <cwchar>