diff --git a/src/os_mswin.c b/src/os_mswin.c
index fc6806d..67989fe 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -1466,8 +1466,8 @@
 	char_u	*port_name = utf16_to_enc(wport_name, NULL);
 
 	if (printer_name != NULL && port_name != NULL)
-	    prt_name = alloc((unsigned)(STRLEN(printer_name)
-					+ STRLEN(port_name) + STRLEN(text)));
+	    prt_name = alloc(STRLEN(printer_name)
+					   + STRLEN(port_name) + STRLEN(text));
 	if (prt_name != NULL)
 	    wsprintf((char *)prt_name, (const char *)text,
 		    printer_name, port_name);
@@ -2111,7 +2111,7 @@
 		char	*err = _(e_invexprmsg);
 		size_t	len = STRLEN(str) + STRLEN(err) + 5;
 
-		res = alloc((unsigned)len);
+		res = alloc(len);
 		if (res != NULL)
 		    vim_snprintf((char *)res, len, "%s: \"%s\"", err, str);
 		reply.dwData = COPYDATA_ERROR_RESULT;
@@ -2340,7 +2340,7 @@
     char_u	*p;
 
     /* Leave enough space for a 9-digit suffix to ensure uniqueness! */
-    ok_name = alloc((unsigned)STRLEN(name) + 10);
+    ok_name = alloc(STRLEN(name) + 10);
 
     STRCPY(ok_name, name);
     p = ok_name + STRLEN(name);