diff --git a/ports/src/lib/libc_noux/plugin.cc b/ports/src/lib/libc_noux/plugin.cc
index 693087592f..39eb88c7f1 100644
--- a/ports/src/lib/libc_noux/plugin.cc
+++ b/ports/src/lib/libc_noux/plugin.cc
@@ -237,7 +237,7 @@ static size_t marshal_fds(fd_set *src_fds, int nfds,
 /**
  * Unmarshal result of select syscall into fd set
  */
-static void unmarshal_fds(int *src_fds, size_t src_fds_len, fd_set *dst_fds)
+static void unmarshal_fds(int nfds, int *src_fds, size_t src_fds_len, fd_set *dst_fds)
 {
 	if (!dst_fds) return;
 
@@ -247,8 +247,13 @@ static void unmarshal_fds(int *src_fds, size_t src_fds_len, fd_set *dst_fds)
 	 * it was allocated dynamically. So we will reset the fd_set manually which
 	 * will work fine as long as we are using FreeBSDs libc - another libc however
 	 * might use a different struct.
+	 *
+	 * Note: The fds are actually stored in a bit-array. So we need to calculate
+	 * how many array entries we have to reset. sizeof (fd_mask) will return the
+	 * size of one entry in bytes.
 	 */
-	for (size_t i = 0; i < src_fds_len; i++)
+	int _ = nfds / (sizeof (fd_mask) * 8) + 1;
+	for (int i = 0; i < _; i++)
 		dst_fds->__fds_bits[i] = 0;
 
 	for (size_t i = 0; i < src_fds_len; i++)
@@ -329,19 +334,19 @@ extern "C" int select(int nfds, fd_set *readfds, fd_set *writefds,
 	int total_fds = 0;
 
 	if (readfds != NULL) {
-		unmarshal_fds(src, out_fds.num_rd, readfds);
+		unmarshal_fds(nfds, src, out_fds.num_rd, readfds);
 		src += out_fds.num_rd;
 		total_fds += out_fds.num_rd;
 	}
 
 	if (writefds != NULL) {
-		unmarshal_fds(src, out_fds.num_wr, writefds);
+		unmarshal_fds(nfds, src, out_fds.num_wr, writefds);
 		src += out_fds.num_wr;
 		total_fds += out_fds.num_wr;
 	}
 
 	if (exceptfds != NULL) {
-		unmarshal_fds(src, out_fds.num_ex, exceptfds);
+		unmarshal_fds(nfds, src, out_fds.num_ex, exceptfds);
 		/* exceptfds are currently ignored */
 	}