diff --git a/win32/clamav-config.h b/win32/clamav-config.h
index 00a44f92ff..03f975f8e1 100644
--- a/win32/clamav-config.h
+++ b/win32/clamav-config.h
@@ -573,7 +573,8 @@
 /* #undef off_t */
 
 /* Define to `int' */
-typedef int ssize_t;
+#include <BaseTsd.h>
+typedef SSIZE_T ssize_t;
 
 /* Define to the equivalent of the C99 'restrict' keyword, or to
    nothing if this is not supported.  Do not define if restrict is
diff --git a/win32/llvmbuild/include/llvm/System/DataTypes.h b/win32/llvmbuild/include/llvm/System/DataTypes.h
index 17323cf911..26cdce3a75 100644
--- a/win32/llvmbuild/include/llvm/System/DataTypes.h
+++ b/win32/llvmbuild/include/llvm/System/DataTypes.h
@@ -109,7 +109,8 @@ typedef short int16_t;
 typedef unsigned short uint16_t;
 typedef signed char int8_t;
 typedef unsigned char uint8_t;
-typedef signed int ssize_t;
+#include <BaseTsd.h>
+typedef SSIZE_T ssize_t;
 /* Certain compatibility updates to VC++ introduce the `cstdint'
 * header, which defines the INT*_C macros. On default installs they
 * are absent. */