diff --git a/src/fileio.c b/src/fileio.c
index 2c6c40e..c87ae4d 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -5351,14 +5351,13 @@
 	    long	nr;
 	    long	off;
 # endif
+	    size_t	itmplen;
 
 	    // Expand $TMP, leave room for "/v1100000/999999999".
 	    // Skip the directory check if the expansion fails.
-	    expand_env((char_u *)tempdirs[i], itmp, TEMPNAMELEN - 20);
+	    itmplen = expand_env((char_u *)tempdirs[i], itmp, TEMPNAMELEN - 20);
 	    if (itmp[0] != '$' && mch_isdir(itmp))
 	    {
-		size_t	itmplen = STRLEN(itmp);
-
 		// directory exists
 		if (!after_pathsep(itmp, itmp + itmplen))
 		{