diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index da37f902c5..601538d8ea 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -4295,11 +4295,26 @@ function attachment_url_to_postid( $url ) {
 	}
 
 	$sql = $wpdb->prepare(
-		"SELECT post_id FROM $wpdb->postmeta WHERE meta_key = '_wp_attached_file' AND meta_value = %s",
+		"SELECT post_id, meta_value FROM $wpdb->postmeta WHERE meta_key = '_wp_attached_file' AND meta_value = %s",
 		$path
 	);
 
-	$post_id = $wpdb->get_var( $sql );
+	$results = $wpdb->get_results( $sql );
+	$post_id = null;
+
+	if ( $results ) {
+		// Use the first available result, but prefer a case-sensitive match, if exists.
+		$post_id = reset( $results )->post_id;
+
+		if ( count( $results ) > 1 ) {
+			foreach ( $results as $result ) {
+				if ( $path === $result->meta_value ) {
+					$post_id = $result->post_id;
+					break;
+				}
+			}
+		}
+	}
 
 	/**
 	 * Filters an attachment id found by URL.
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 26d8468bc2..9b99cf9106 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -1058,7 +1058,10 @@ VIDEO;
 		$this->assertEquals( $attachment_id, attachment_url_to_postid( $image_url ) );
 	}
 
-	function test_attachment_url_to_postid_schemes() {
+	/**
+	 * @ticket 33109
+	 */
+	function test_attachment_url_to_postid_with_different_scheme() {
 		$image_path    = '2014/11/' . $this->img_name;
 		$attachment_id = self::factory()->attachment->create_object(
 			$image_path,
@@ -1069,13 +1072,38 @@ VIDEO;
 			)
 		);
 
-		/**
-		 * @ticket 33109 Testing protocols not matching
-		 */
 		$image_url = 'https://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . $image_path;
 		$this->assertEquals( $attachment_id, attachment_url_to_postid( $image_url ) );
 	}
 
+	/**
+	 * @ticket 39768
+	 */
+	function test_attachment_url_to_postid_should_be_case_sensitive() {
+		$image_path_lower_case    = '2014/11/' . $this->img_name;
+		$attachment_id_lower_case = self::factory()->attachment->create_object(
+			$image_path_lower_case,
+			0,
+			array(
+				'post_mime_type' => 'image/jpeg',
+				'post_type'      => 'attachment',
+			)
+		);
+
+		$image_path_upper_case    = '2014/11/' . ucfirst( $this->img_name );
+		$attachment_id_upper_case = self::factory()->attachment->create_object(
+			$image_path_upper_case,
+			0,
+			array(
+				'post_mime_type' => 'image/jpeg',
+				'post_type'      => 'attachment',
+			)
+		);
+
+		$image_url = 'http://' . WP_TESTS_DOMAIN . '/wp-content/uploads/' . $image_path_upper_case;
+		$this->assertEquals( $attachment_id_upper_case, attachment_url_to_postid( $image_url ) );
+	}
+
 	function test_attachment_url_to_postid_filtered() {
 		$image_path    = '2014/11/' . $this->img_name;
 		$attachment_id = self::factory()->attachment->create_object(