diff --git a/src/include/slirp/libslirp.h b/src/include/slirp/libslirp.h
index 27e1f61bb..7c4340390 100644
--- a/src/include/slirp/libslirp.h
+++ b/src/include/slirp/libslirp.h
@@ -16,6 +16,17 @@
 
 #include "libslirp-version.h"
 
+/* Windows does not define ssize_t, so we need to define it here. */
+#ifndef _SSIZE_T_DEFINED
+# define _SSIZE_T_DEFINED
+# undef ssize_t
+# ifdef _WIN64
+#  define ssize_t int64_t
+# else
+#  define ssize_t int32_t
+# endif
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/include/tinyglib.h b/src/include/tinyglib.h
index e510cbc85..fabdefcfc 100644
--- a/src/include/tinyglib.h
+++ b/src/include/tinyglib.h
@@ -77,6 +77,17 @@
 
 /* Types */
 
+/* Windows does not define ssize_t, so we need to define it here. */
+#ifndef _SSIZE_T_DEFINED
+# define _SSIZE_T_DEFINED
+# undef ssize_t
+# ifdef _WIN64
+#  define ssize_t int64_t
+# else
+#  define ssize_t int32_t
+# endif
+#endif
+
 #define gboolean int
 #define gchar char
 #define gint int
diff --git a/src/network/slirp/libslirp.h b/src/network/slirp/libslirp.h
index 27e1f61bb..7c4340390 100644
--- a/src/network/slirp/libslirp.h
+++ b/src/network/slirp/libslirp.h
@@ -16,6 +16,17 @@
 
 #include "libslirp-version.h"
 
+/* Windows does not define ssize_t, so we need to define it here. */
+#ifndef _SSIZE_T_DEFINED
+# define _SSIZE_T_DEFINED
+# undef ssize_t
+# ifdef _WIN64
+#  define ssize_t int64_t
+# else
+#  define ssize_t int32_t
+# endif
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif