diff --git a/PC/config.h b/PC/config.h
index 495b98574fe3..b043df530ba2 100644
--- a/PC/config.h
+++ b/PC/config.h
@@ -211,6 +211,7 @@ typedef int pid_t;
 
 #define SIZEOF_INT 4
 #define SIZEOF_LONG 4
+#define SIZEOF_LONG_LONG 8
 
 /* EXPERIMENTAL FEATURE: When CHECK_IMPORT_CASE is defined, check case of
    imported modules against case of file; this causes "import String" to fail