diff --git a/coreutils/df.c b/coreutils/df.c
index cbe316920..708e12cc0 100644
--- a/coreutils/df.c
+++ b/coreutils/df.c
@@ -143,7 +143,7 @@ extern int df_main(int argc, char **argv)
 			if (strcmp(device, "/dev/root") == 0) {
 				/* Adjusts device to be the real root device,
 				* or leaves device alone if it can't find it */
-				if ((device = find_real_root_device_name(device)) != NULL) {
+				if ((device = find_real_root_device_name(device)) == NULL) {
 					goto SET_ERROR;
 				}
 			}