diff --git a/src/json.hpp b/src/json.hpp
index 95bfe9de..3633151d 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -38,6 +38,7 @@
 
 // enable ssize_t for MSVC
 #ifdef _MSC_VER
+    #include <basetsd.h>
     using ssize_t = SSIZE_T;
 #endif
 
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index a6f02baa..0468076f 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -38,6 +38,7 @@
 
 // enable ssize_t for MSVC
 #ifdef _MSC_VER
+    #include <basetsd.h>
     using ssize_t = SSIZE_T;
 #endif