diff --git a/contracts/token/ERC721/ERC721.sol b/contracts/token/ERC721/ERC721.sol
index 4232c616eb7..fcaf04f2afb 100644
--- a/contracts/token/ERC721/ERC721.sol
+++ b/contracts/token/ERC721/ERC721.sol
@@ -114,9 +114,6 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      */
     function approve(address to, uint256 tokenId) public virtual {
         address owner = ownerOf(tokenId);
-        if (to == owner) {
-            revert ERC721InvalidOperator(owner);
-        }
 
         if (_msgSender() != owner && !isApprovedForAll(owner, _msgSender())) {
             revert ERC721InvalidApprover(_msgSender());
@@ -131,7 +128,7 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
     function getApproved(uint256 tokenId) public view virtual returns (address) {
         _requireMinted(tokenId);
 
-        return _tokenApprovals[tokenId];
+        return _getApproved(tokenId);
     }
 
     /**
@@ -220,16 +217,22 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
         return _ownerOf(tokenId) != address(0);
     }
 
+    /**
+     * @dev Returns the approved address for `tokenId`. Returns 0 if `tokenId` is not minted.
+     */
+    function _getApproved(uint256 tokenId) internal view virtual returns (address) {
+        return _tokenApprovals[tokenId];
+    }
+
     /**
      * @dev Returns whether `spender` is allowed to manage `tokenId`.
-     *
-     * Requirements:
-     *
-     * - `tokenId` must exist.
      */
     function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
-        address owner = ownerOf(tokenId);
-        return (spender == owner || isApprovedForAll(owner, spender) || getApproved(tokenId) == spender);
+        address owner = _ownerOf(tokenId);
+        return (owner != address(0) &&
+            (spender == owner ||
+                isApprovedForAll(owner, spender) ||
+                (_getApproved(tokenId) == spender && spender != address(0))));
     }
 
     /**
@@ -386,8 +389,12 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      * Emits an {Approval} event.
      */
     function _approve(address to, uint256 tokenId) internal virtual {
+        address owner = ownerOf(tokenId);
+        if (to == owner || to == address(0)) {
+            revert ERC721InvalidOperator(to);
+        }
         _tokenApprovals[tokenId] = to;
-        emit Approval(ownerOf(tokenId), to, tokenId);
+        emit Approval(owner, to, tokenId);
     }
 
     /**
@@ -396,8 +403,8 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      * Emits an {ApprovalForAll} event.
      */
     function _setApprovalForAll(address owner, address operator, bool approved) internal virtual {
-        if (owner == operator) {
-            revert ERC721InvalidOperator(owner);
+        if (operator == owner || operator == address(0)) {
+            revert ERC721InvalidOperator(operator);
         }
         _operatorApprovals[owner][operator] = approved;
         emit ApprovalForAll(owner, operator, approved);