diff --git a/lib/dml/mssql_native_moodle_database.php b/lib/dml/mssql_native_moodle_database.php
index cc682e5cb82..f45d05ee4da 100644
--- a/lib/dml/mssql_native_moodle_database.php
+++ b/lib/dml/mssql_native_moodle_database.php
@@ -327,7 +327,7 @@ class mssql_native_moodle_database extends moodle_database {
         if ($result) {
             while ($row = mssql_fetch_row($result)) {
                 $tablename = reset($row);
-                if ($this->prefix !== '') {
+                if ($this->prefix !== false && $this->prefix !== '') {
                     if (strpos($tablename, $this->prefix) !== 0) {
                         continue;
                     }
diff --git a/lib/dml/oci_native_moodle_database.php b/lib/dml/oci_native_moodle_database.php
index 502a266b157..5a158020061 100644
--- a/lib/dml/oci_native_moodle_database.php
+++ b/lib/dml/oci_native_moodle_database.php
@@ -406,7 +406,7 @@ class oci_native_moodle_database extends moodle_database {
         oci_free_statement($stmt);
         $records = array_map('strtolower', $records['TABLE_NAME']);
         foreach ($records as $tablename) {
-            if ($this->prefix !== '') {
+            if ($this->prefix !== false && $this->prefix !== '') {
                 if (strpos($tablename, $this->prefix) !== 0) {
                     continue;
                 }
diff --git a/lib/dml/pgsql_native_moodle_database.php b/lib/dml/pgsql_native_moodle_database.php
index f4cf21dd0e7..64dcc24a5c3 100644
--- a/lib/dml/pgsql_native_moodle_database.php
+++ b/lib/dml/pgsql_native_moodle_database.php
@@ -320,7 +320,7 @@ class pgsql_native_moodle_database extends moodle_database {
         if ($result) {
             while ($row = pg_fetch_row($result)) {
                 $tablename = reset($row);
-                if ($this->prefix !== '') {
+                if ($this->prefix !== false && $this->prefix !== '') {
                     if (strpos($tablename, $this->prefix) !== 0) {
                         continue;
                     }
diff --git a/lib/dml/sqlite3_pdo_moodle_database.php b/lib/dml/sqlite3_pdo_moodle_database.php
index 7828eb7162f..fcfe446df81 100644
--- a/lib/dml/sqlite3_pdo_moodle_database.php
+++ b/lib/dml/sqlite3_pdo_moodle_database.php
@@ -150,7 +150,7 @@ class sqlite3_pdo_moodle_database extends pdo_moodle_database {
         foreach ($rstables as $table) {
             $table = $table['name'];
             $table = strtolower($table);
-            if ($this->prefix !== '') {
+            if ($this->prefix !== false && $this->prefix !== '') {
                 if (strpos($table, $this->prefix) !== 0) {
                     continue;
                 }
diff --git a/lib/dml/sqlsrv_native_moodle_database.php b/lib/dml/sqlsrv_native_moodle_database.php
index 093cda6ae66..9521affb460 100644
--- a/lib/dml/sqlsrv_native_moodle_database.php
+++ b/lib/dml/sqlsrv_native_moodle_database.php
@@ -380,7 +380,7 @@ class sqlsrv_native_moodle_database extends moodle_database {
         if ($result) {
             while ($row = sqlsrv_fetch_array($result)) {
                 $tablename = reset($row);
-                if ($this->prefix !== '') {
+                if ($this->prefix !== false && $this->prefix !== '') {
                     if (strpos($tablename, $this->prefix) !== 0) {
                         continue;
                     }