diff --git a/src/modbus-private.h b/src/modbus-private.h
index ea83187f..f108fe6f 100644
--- a/src/modbus-private.h
+++ b/src/modbus-private.h
@@ -14,8 +14,10 @@
 #else
 # include "stdint.h"
 # include <time.h>
+#ifndef ssize_t
 typedef int ssize_t;
 #endif
+#endif
 // clang-format on
 #include <config.h>
 #include <sys/types.h>