diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index b2f8fec..97983ef 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -239,6 +239,32 @@
   END
 enddef
 
+let g:someNumber = 43
+
+def Test_assign_concat()
+  var lines =<< trim END
+    var s = '-'
+    s ..= 99
+    s ..= true
+    s ..= '-'
+    s ..= v:null
+    s ..= g:someNumber
+    assert_equal('-99true-null43', s)
+  END
+  CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+    var s = '-'
+    s ..= [1, 2]
+  END
+  CheckDefAndScriptFailure2(lines, 'E1105: Cannot convert list to string', 'E734: Wrong variable type for .=', 2)
+  lines =<< trim END
+    var s = '-'
+    s ..= {a: 2}
+  END
+  CheckDefAndScriptFailure2(lines, 'E1105: Cannot convert dict to string', 'E734: Wrong variable type for .=', 2)
+enddef
+
 def Test_assign_register()
   var lines =<< trim END
     @c = 'areg'
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 1d100e0..b151cb4 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -1254,7 +1254,7 @@
         'res ..= str\_s*' ..
         '\d\+ LOAD $0\_s*' ..
         '\d\+ LOAD $2\_s*' ..
-        '\d\+ CHECKTYPE string stack\[-1\]\_s*' ..
+        '\d 2STRING_ANY stack\[-1\]\_s*' ..
         '\d\+ CONCAT\_s*' ..
         '\d\+ STORE $0\_s*' ..
         'endfor\_s*' ..
diff --git a/src/version.c b/src/version.c
index fcfd211..76c3e97 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3263,
+/**/
     3262,
 /**/
     3261,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index c6a2965..cafbd6b 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -7086,18 +7086,23 @@
 	    type_T	    *stacktype;
 
 	    if (*op == '.')
-		expected = &t_string;
+	    {
+		if (may_generate_2STRING(-1, FALSE, cctx) == FAIL)
+		    goto theend;
+	    }
 	    else
+	    {
 		expected = lhs.lhs_member_type;
-	    stacktype = ((type_T **)stack->ga_data)[stack->ga_len - 1];
-	    if (
+		stacktype = ((type_T **)stack->ga_data)[stack->ga_len - 1];
+		if (
 #ifdef FEAT_FLOAT
-		// If variable is float operation with number is OK.
-		!(expected == &t_float && stacktype == &t_number) &&
+		    // If variable is float operation with number is OK.
+		    !(expected == &t_float && stacktype == &t_number) &&
 #endif
 		    need_type(stacktype, expected, -1, 0, cctx,
 							 FALSE, FALSE) == FAIL)
-		goto theend;
+		    goto theend;
+	    }
 
 	    if (*op == '.')
 	    {