diff --git a/src/eval.c b/src/eval.c
index bf01ae0..6b12a97 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2849,11 +2849,12 @@
 	int	    vim9script = in_vim9script();
 
 	// "." is only string concatenation when scriptversion is 1
-	// "+=" and "-=" are assignment
+	// "+=", "-=" and "..=" are assignments
 	p = eval_next_non_blank(*arg, evalarg, &getnext);
 	op = *p;
 	concat = op == '.' && (*(p + 1) == '.' || current_sctx.sc_version < 2);
-	if ((op != '+' && op != '-' && !concat) || p[1] == '=')
+	if ((op != '+' && op != '-' && !concat) || p[1] == '='
+					       || (p[1] == '.' && p[2] == '='))
 	    break;
 
 	evaluate = evalarg == NULL ? 0 : (evalarg->eval_flags & EVAL_EVALUATE);
@@ -3080,9 +3081,10 @@
 #endif
 	int	    error;
 
+	// "*=", "/=" and "%=" are assignments
 	p = eval_next_non_blank(*arg, evalarg, &getnext);
 	op = *p;
-	if (op != '*' && op != '/' && op != '%')
+	if ((op != '*' && op != '/' && op != '%') || p[1] == '=')
 	    break;
 
 	evaluate = evalarg == NULL ? 0 : (evalarg->eval_flags & EVAL_EVALUATE);