diff --git a/src/strtonum.c b/src/strtonum.c
index f5e35b9..a593c10 100644
--- a/src/strtonum.c
+++ b/src/strtonum.c
@@ -23,6 +23,7 @@
 #include <errno.h>
 #include <limits.h>
 #include <stdlib.h>
+#include "strtonum.h"
 
 #define INVALID 1
 #define TOOSMALL 2
diff --git a/src/strtonum.h b/src/strtonum.h
new file mode 100644
index 0000000..c063101
--- /dev/null
+++ b/src/strtonum.h
@@ -0,0 +1,16 @@
+/* Copyright (c) 2019, Michael Santos <michael.santos@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+long long strtonum(const char *numstr, long long minval, long long maxval,
+                   const char **errstrp);
diff --git a/src/xmppipe.h b/src/xmppipe.h
index 3bcb343..ad6b676 100644
--- a/src/xmppipe.h
+++ b/src/xmppipe.h
@@ -23,6 +23,10 @@
 
 #include <strophe.h>
 
+#ifndef HAVE_STRTONUM
+#include "strtonum.h"
+#endif
+
 #define XMPPIPE_VERSION "0.12.0"
 #define XMPPIPE_RESOURCE "xmppipe"
 
@@ -167,8 +171,3 @@ int xmppipe_conn_fd(xmppipe_state_t *state);
 int b64_ntop(u_char const *src, size_t srclength, char *target,
              size_t targsize);
 int b64_pton(char const *src, u_char *target, size_t targsize);
-
-#ifndef HAVE_STRTONUM
-long long strtonum(const char *numstr, long long minval, long long maxval,
-                   const char **errstrp);
-#endif