diff --git a/source/lib/sysdep/os/win/wposix/wposix_types.h b/source/lib/sysdep/os/win/wposix/wposix_types.h
index 58afcd6c0e..3b52051dd9 100644
--- a/source/lib/sysdep/os/win/wposix/wposix_types.h
+++ b/source/lib/sysdep/os/win/wposix/wposix_types.h
@@ -34,7 +34,7 @@
 // <inttypes.h>
 //
 
-typedef __int8 int8_t;
+typedef signed char int8_t;
 typedef short int16_t;
 
 // already defined by MinGW
diff --git a/source/scriptinterface/ScriptTypes.h b/source/scriptinterface/ScriptTypes.h
index c73f8a9119..c7a68a086e 100644
--- a/source/scriptinterface/ScriptTypes.h
+++ b/source/scriptinterface/ScriptTypes.h
@@ -27,6 +27,10 @@
 // non-struct type instead
 # define JS_NO_JSVAL_JSID_STRUCT_TYPES
 
+// Make JS think the int8_t etc types are defined, since wposix_types.h emulates
+// the ones that are needed and this avoids conflicting definitions
+# define JS_SYS_TYPES_H_DEFINES_EXACT_SIZE_TYPES
+
 #else
 # define XP_UNIX
 #endif