diff --git a/files/classes/conversion.php b/files/classes/conversion.php
index 0a2e8610ed5..ffe01d1ce81 100644
--- a/files/classes/conversion.php
+++ b/files/classes/conversion.php
@@ -128,36 +128,13 @@ class conversion extends \core\persistent {
 
         // Fetch actual conversions which relate to the specified source file, and have a matching conversion record,
         // and either have a valid destination file which still exists, or do not have a destination file at all.
-        $dbfamily = $DB->get_dbfamily();
-        switch ($dbfamily) {
-            // For certain DB engines, use a more optimised query.
-            case 'mysql':
-            case 'postgres':
-                $sql = "SELECT {$sqlfields}
-                          FROM {" . self::TABLE . "} c
-                          JOIN (SELECT id
-                                  FROM {files}
-                                 WHERE contenthash = :ccontenthash
-                                 LIMIT 1
-                               ) conversionsourcefile ON conversionsourcefile.id = c.sourcefileid
-                     LEFT JOIN {files} conversiondestfile ON conversiondestfile.id = c.destfileid
-                         WHERE c.targetformat = :cformat
-                           AND (c.destfileid IS NULL
-                                OR conversiondestfile.id IS NOT NULL)";
-                break;
-
-            // For everything else, use the standard cross-db compatible query.
-            default:
-                $sql = "SELECT {$sqlfields}
-                          FROM {" . self::TABLE . "} c
-                    INNER JOIN {files} conversionsourcefile ON conversionsourcefile.id = c.sourcefileid
-                     LEFT JOIN {files} conversiondestfile ON conversiondestfile.id = c.destfileid
-                         WHERE conversionsourcefile.contenthash = :ccontenthash
-                           AND c.targetformat = :cformat
-                           AND (c.destfileid IS NULL
-                                OR conversiondestfile.id IS NOT NULL)";
-                break;
-        }
+        $sql = "SELECT {$sqlfields}
+                  FROM {" . self::TABLE . "} c
+                  JOIN {files} conversionsourcefile ON conversionsourcefile.id = c.sourcefileid
+             LEFT JOIN {files} conversiondestfile ON conversiondestfile.id = c.destfileid
+                 WHERE conversionsourcefile.contenthash = :ccontenthash
+                       AND c.targetformat = :cformat
+                       AND (c.destfileid IS NULL OR conversiondestfile.id IS NOT NULL)";
 
         // Fetch a empty conversion record for each source/destination combination that we find to match where the
         // destination file is in the correct filearea/filepath/filename combination to meet the requirements.
@@ -193,7 +170,6 @@ class conversion extends \core\persistent {
         $records = $DB->get_records_sql($sql, [
             'ccontenthash' => $file->get_contenthash(),
             'osourcefileid' => $file->get_id(),
-            'cfilepath' => "/{$format}/",
             'ofilepath' => "/{$format}/",
             'cformat' => $format,
             'oformat' => $format,
diff --git a/files/tests/conversion_test.php b/files/tests/conversion_test.php
index 07b1f2669ca..1cacf28e0e2 100644
--- a/files/tests/conversion_test.php
+++ b/files/tests/conversion_test.php
@@ -75,6 +75,53 @@ class conversion_test extends \advanced_testcase {
         $this->assertFalse($conversion->get_destfile());
     }
 
+    /**
+     * Ensure that get_conversions_for_file returns an existing conversion
+     * record with matching sourcefileid and targetformat when a file with the same
+     * contenthash is uploaded several times.
+     *
+     * @covers \core_files\conversion::get_conversions_for_file
+     */
+    public function test_get_conversions_for_multiple_files_existing_conversion_incomplete() {
+        $this->resetAfterTest();
+
+        // Create a bunch of files with the same content.
+        for ($i = 0; $i < 5; $i++) {
+            $sourcefiles[] = $this->create_stored_file('test content', 'testfile' . $i . '.txt');
+        }
+
+        // Use only one file for the conversion.
+        // Pick some file in the middle.
+        $sourcefile = $sourcefiles[count($sourcefiles) - 2];
+
+        $existing = new conversion(0, (object) [
+            'sourcefileid' => $sourcefile->get_id(),
+            'targetformat' => 'pdf',
+        ]);
+        $existing->create();
+
+        $conversions = conversion::get_conversions_for_file($sourcefile, 'pdf');
+        $this->assertCount(1, $conversions);
+
+        $conversion = array_shift($conversions);
+        $conversionfile = $conversion->get_sourcefile();
+
+        $this->assertEquals($sourcefile->get_id(), $conversionfile->get_id());
+        $this->assertFalse($conversion->get_destfile());
+
+        // Check that getting the conversion for a different file record with the same contenthash
+        // returns the same conversion as above.
+        $conversions = conversion::get_conversions_for_file($sourcefiles[count($sourcefiles) - 1], 'pdf');
+        $this->assertCount(1, $conversions);
+
+        $conversion = array_shift($conversions);
+        $conversionfile = $conversion->get_sourcefile();
+
+        $this->assertEquals($existing->get('id'), $conversion->get('id'));
+        $this->assertEquals($sourcefile->get_id(), $conversionfile->get_id());
+        $this->assertFalse($conversion->get_destfile());
+    }
+
     /**
      * Ensure that get_conversions_for_file returns an existing conversion
      * record with matching sourcefileid and targetformat when a second
@@ -139,6 +186,7 @@ class conversion_test extends \advanced_testcase {
 
         $conversion = array_shift($conversions);
 
+        $this->assertEquals($existing->get('id'), $conversion->get('id'));
         $this->assertEquals($sourcefile->get_id(), $conversion->get_sourcefile()->get_id());
         $this->assertEquals($destfile->get_id(), $conversion->get_destfile()->get_id());
     }