diff --git a/changes/bug4691 b/changes/bug4691
new file mode 100644
index 0000000000..124b8f8ab9
--- /dev/null
+++ b/changes/bug4691
@@ -0,0 +1,4 @@
+  o Major bugfixes:
+    - Fix compilation of the libnatpmp helper on non-Windows. Bugfix on
+      0.2.3.9-alpha; fixes bug 4691. Reported by Anthony G. Basile.
+
diff --git a/src/tools/tor-fw-helper/tor-fw-helper-natpmp.c b/src/tools/tor-fw-helper/tor-fw-helper-natpmp.c
index aaa685e1ee..2380b141df 100644
--- a/src/tools/tor-fw-helper/tor-fw-helper-natpmp.c
+++ b/src/tools/tor-fw-helper/tor-fw-helper-natpmp.c
@@ -16,6 +16,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#ifndef MS_WINDOWS
+#include <arpa/inet.h>
+#endif
 
 // debugging stuff
 #include <assert.h>