diff --git a/src/internal/slibtool_realpath_impl.c b/src/internal/slibtool_realpath_impl.c
index 4e586a8..63fc3c4 100644
--- a/src/internal/slibtool_realpath_impl.c
+++ b/src/internal/slibtool_realpath_impl.c
@@ -18,6 +18,7 @@
 
 #ifdef HAVE_SYS_SYSCALL_H
 #include <sys/syscall.h>
+#include <unistd.h>
 #endif
 
 #ifdef _MIDIPIX_ABI
@@ -28,10 +29,6 @@
 #define ENOTSUP EOPNOTSUPP
 #endif
 
-#ifdef SYS___realpathat
-extern long syscall(int, ...);
-#endif
-
 slbt_hidden int slbt_realpath(
 	int             fdat,
 	const char *    path,