diff --git a/src/libfast/fast_request.c b/src/libfast/fast_request.c
index 0543215cb..5f6e39281 100644
--- a/src/libfast/fast_request.c
+++ b/src/libfast/fast_request.c
@@ -25,6 +25,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <inttypes.h>
 
 #include <ClearSilver/ClearSilver.h>
 
@@ -303,7 +304,7 @@ METHOD(fast_request_t, sendfile, bool,
 		return FALSE;
 	}
 	/* FCGX does not like large integers, print to a buffer using libc */
-	snprintf(buf, sizeof(buf), "%lld", (int64_t)data->len);
+	snprintf(buf, sizeof(buf), "%"PRId64, (int64_t)data->len);
 	FCGX_FPrintF(this->req.out, "Content-Length: %s\n", buf);
 	if (mime)
 	{