diff --git a/src/os/unix/ngx_freebsd_config.h b/src/os/unix/ngx_freebsd_config.h
index 31602f8..7ec14a6 100644
--- a/src/os/unix/ngx_freebsd_config.h
+++ b/src/os/unix/ngx_freebsd_config.h
@@ -5,6 +5,7 @@
 #include <unistd.h>
 #include <stddef.h>             /* offsetof */
 #include <stdlib.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <signal.h>
diff --git a/src/os/unix/ngx_linux_config.h b/src/os/unix/ngx_linux_config.h
index 9056657..6055cc6 100644
--- a/src/os/unix/ngx_linux_config.h
+++ b/src/os/unix/ngx_linux_config.h
@@ -11,6 +11,7 @@
 #include <unistd.h>
 #include <stddef.h>             /* offsetof */
 #include <stdlib.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <signal.h>
diff --git a/src/os/unix/ngx_solaris_config.h b/src/os/unix/ngx_solaris_config.h
index a5b66c4..43423aa 100644
--- a/src/os/unix/ngx_solaris_config.h
+++ b/src/os/unix/ngx_solaris_config.h
@@ -11,6 +11,7 @@
 #include <unistd.h>
 #include <stddef.h>             /* offsetof */
 #include <stdlib.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <signal.h>