diff --git a/VM/src/lstrlib.cpp b/VM/src/lstrlib.cpp
index 69fd0d67..49158f27 100644
--- a/VM/src/lstrlib.cpp
+++ b/VM/src/lstrlib.cpp
@@ -1034,6 +1034,11 @@ static int str_format(lua_State* L)
             }
             case '*':
             {
+                if (formatItemSize != 1)
+                {
+                    luaL_error(L, "'%%*' does not take a form");
+                }
+
                 size_t length;
                 const char* string = luaL_tolstring(L, arg, &length);
 
diff --git a/tests/conformance/strings.lua b/tests/conformance/strings.lua
index f07fb4bd..c87cf15c 100644
--- a/tests/conformance/strings.lua
+++ b/tests/conformance/strings.lua
@@ -146,6 +146,10 @@ end) == false)
 assert(string.format("%*", "a\0b\0c") == "a\0b\0c")
 assert(string.format("%*", string.rep("doge", 3000)) == string.rep("doge", 3000))
 
+assert(pcall(function()
+	string.format("%#*", "bad form")
+end) == false)
+
 assert(loadstring("return 1\n--comentário sem EOL no final")() == 1)