diff --git a/Src/parse.c b/Src/parse.c
index b09c7989a..153633bb1 100644
--- a/Src/parse.c
+++ b/Src/parse.c
@@ -1525,10 +1525,16 @@ par_while(int *cmplx)
     incmdpos = 1;
     while (tok == SEPER)
 	zshlex();
-    if (tok == DOLOOP) {
+    /*
+     * If the very first thing after "while" is "do",
+     * ecused has advanced only two positions.  This
+     * is not a valid while-do construction.
+     */
+    if (tok == DOLOOP && (ecused - oecused) > 2) {
 	zshlex();
 	par_save_list(cmplx);
-	if (tok != DONE)
+	/* As above but "do done" is not valid */
+	if (tok != DONE || (ecused - oecused) < 8)
 	    YYERRORV(oecused);
 	incmdpos = 0;
 	zshlex();