diff --git a/datasette/app.py b/datasette/app.py
index 5976d8b8..5f348cb5 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -224,6 +224,7 @@ class Datasette:
         self.inspect_data = inspect_data
         self.immutables = set(immutables or [])
         self.databases = collections.OrderedDict()
+        self._refresh_schemas_lock = asyncio.Lock()
         self.crossdb = crossdb
         if memory or crossdb or not self.files:
             self.add_database(Database(self, is_memory=True), name="_memory")
@@ -332,6 +333,12 @@ class Datasette:
         self.client = DatasetteClient(self)
 
     async def refresh_schemas(self):
+        if self._refresh_schemas_lock.locked():
+            return
+        async with self._refresh_schemas_lock:
+            await self._refresh_schemas()
+
+    async def _refresh_schemas(self):
         internal_db = self.databases["_internal"]
         if not self.internal_db_created:
             await init_internal_db(internal_db)
diff --git a/datasette/utils/internal_db.py b/datasette/utils/internal_db.py
index e92625d5..40fe719e 100644
--- a/datasette/utils/internal_db.py
+++ b/datasette/utils/internal_db.py
@@ -5,7 +5,7 @@ async def init_internal_db(db):
     await db.execute_write(
         textwrap.dedent(
             """
-    CREATE TABLE databases (
+    CREATE TABLE IF NOT EXISTS databases (
         database_name TEXT PRIMARY KEY,
         path TEXT,
         is_memory INTEGER,
@@ -18,7 +18,7 @@ async def init_internal_db(db):
     await db.execute_write(
         textwrap.dedent(
             """
-    CREATE TABLE tables (
+    CREATE TABLE IF NOT EXISTS tables (
         database_name TEXT,
         table_name TEXT,
         rootpage INTEGER,
@@ -33,7 +33,7 @@ async def init_internal_db(db):
     await db.execute_write(
         textwrap.dedent(
             """
-    CREATE TABLE columns (
+    CREATE TABLE IF NOT EXISTS columns (
         database_name TEXT,
         table_name TEXT,
         cid INTEGER,
@@ -54,7 +54,7 @@ async def init_internal_db(db):
     await db.execute_write(
         textwrap.dedent(
             """
-    CREATE TABLE indexes (
+    CREATE TABLE IF NOT EXISTS indexes (
         database_name TEXT,
         table_name TEXT,
         seq INTEGER,
@@ -73,7 +73,7 @@ async def init_internal_db(db):
     await db.execute_write(
         textwrap.dedent(
             """
-    CREATE TABLE foreign_keys (
+    CREATE TABLE IF NOT EXISTS foreign_keys (
         database_name TEXT,
         table_name TEXT,
         id INTEGER,