diff --git a/src/eval.c b/src/eval.c
index 78e2c60..9e93dcf 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1249,6 +1249,7 @@
     char_u	op[2];
     char_u	*argend;
     int		first = TRUE;
+    int		concat;
 
     argend = skip_var_list(arg, &var_count, &semicolon);
     if (argend == NULL)
@@ -1256,14 +1257,19 @@
     if (argend > arg && argend[-1] == '.')  // for var.='str'
 	--argend;
     expr = skipwhite(argend);
-    if (*expr != '=' && !((vim_strchr((char_u *)"+-*/%.", *expr) != NULL
-			   && expr[1] == '=') || STRNCMP(expr, "..=", 3) == 0))
+    concat = expr[0] == '.'
+	&& ((expr[1] == '=' && current_sctx.sc_version < 2)
+		|| (expr[1] == '.' && expr[2] == '='));
+    if (*expr != '=' && !((vim_strchr((char_u *)"+-*/%", *expr) != NULL
+						 && expr[1] == '=') || concat))
     {
 	/*
 	 * ":let" without "=": list variables
 	 */
 	if (*arg == '[')
 	    emsg(_(e_invarg));
+	else if (expr[0] == '.')
+	    emsg(_("E985: .= is not supported with script version 2"));
 	else if (!ends_excmd(*arg))
 	    /* ":let var1 var2" */
 	    arg = list_arg_vars(eap, arg, &first);
@@ -3817,7 +3823,7 @@
  * Handle fourth level expression:
  *	+	number addition
  *	-	number subtraction
- *	.	string concatenation
+ *	.	string concatenation (if script version is 1)
  *	..	string concatenation
  *
  * "arg" must point to the first non-white of the expression.
@@ -3838,6 +3844,7 @@
     char_u	*s1, *s2;
     char_u	buf1[NUMBUFLEN], buf2[NUMBUFLEN];
     char_u	*p;
+    int		concat;
 
     /*
      * Get the first variable.
@@ -3850,8 +3857,11 @@
      */
     for (;;)
     {
+	// "." is only string concatenation when scriptversion is 1
 	op = **arg;
-	if (op != '+' && op != '-' && op != '.')
+	concat = op == '.'
+			&& (*(*arg + 1) == '.' || current_sctx.sc_version < 2);
+	if (op != '+' && op != '-' && !concat)
 	    break;
 
 	if ((op != '+' || (rettv->v_type != VAR_LIST
@@ -4224,6 +4234,17 @@
 	*arg = skipwhite(*arg + 1);
     end_leader = *arg;
 
+    if (**arg == '.' && (!isdigit(*(*arg + 1))
+#ifdef FEAT_FLOAT
+	    || current_sctx.sc_version < 2
+#endif
+	    ))
+    {
+	semsg(_(e_invexpr2), *arg);
+	++*arg;
+	return FAIL;
+    }
+
     switch (**arg)
     {
     /*
@@ -4239,16 +4260,23 @@
     case '7':
     case '8':
     case '9':
+    case '.':
 	{
 #ifdef FEAT_FLOAT
-		char_u *p = skipdigits(*arg + 1);
+		char_u *p;
 		int    get_float = FALSE;
 
 		/* We accept a float when the format matches
 		 * "[0-9]\+\.[0-9]\+\([eE][+-]\?[0-9]\+\)\?".  This is very
 		 * strict to avoid backwards compatibility problems.
+		 * With script version 2 and later the leading digit can be
+		 * omitted.
 		 * Don't look for a float after the "." operator, so that
 		 * ":let vers = 1.2.3" doesn't fail. */
+		if (**arg == '.')
+		    p = *arg;
+		else
+		    p = skipdigits(*arg + 1);
 		if (!want_string && p[0] == '.' && vim_isdigit(p[1]))
 		{
 		    get_float = TRUE;