The spell now requires a melee weapon worth 1sp. You can use objects as improvised weapons, but they are not weapons. As another answer states,
An improvised weapon is, indeed, a weapon, but only the moment it's used as such. A chair/shield/etc isn't a weapon otherwise.
Melee weapons can be found in the weapons table in the PHB. A rock is not a weapon. A gold bar is not a weapon. When you cast the spell, the chair in your hand is not a weapon.
... but your DM can rule otherwise.
A DM can surely rule that such objects count as blunt weapons, and would therefore work as long as their value is over 1sp. I wouldn't do it at my table unless the character something that could realistically emulate a weapon (like an expensive knife could be a Dagger), but to each their own.
In many cases, an improvised weapon is similar to an actual weapon and can be treated as such. For example, a table leg is akin to a club. At the DM’s option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.
However, if you think that treating any object as a potential weapon would make the game more fun, discuss with your DM and come to a general conclusion.