Fixed typo.

diff --git a/win32/code_page.c b/win32/code_page.c
index 6e89be1..b59494f 100644
--- a/win32/code_page.c
+++ b/win32/code_page.c
@@ -182,7 +182,7 @@
     int care_for_eos=0;
     int dont_copy= (dstlen==0);
 
-    if ((!src) | ((!dst) && (!dont_copy)) )
+    if ((!src) || ((!dst) && (!dont_copy)) )
     {	SetLastError(ERROR_INVALID_PARAMETER);
 	return 0;
     }