diff --git a/workpackages/remapping.py b/workpackages/remapping.py
index 89e5910..a26545c 100644
--- a/workpackages/remapping.py
+++ b/workpackages/remapping.py
@@ -117,7 +117,7 @@ def remap_table_wp_to_master(cursor, table_name, wp_name, new_master_fid):
     wp_fids_missing = set()
     sql = (
         f"""SELECT {pkey_column_escaped} FROM {table_name_escaped} """
-        f"""LEFT JOIN {remap_table} AS mapped ON fid = mapped.wp_fid WHERE mapped.master_fid IS NULL"""
+        f"""LEFT JOIN {remap_table} AS mapped ON {pkey_column_escaped} = mapped.wp_fid WHERE mapped.master_fid IS NULL"""
     )
     for row in cursor.execute(sql):
         wp_fids_missing.add(row[0])
@@ -131,7 +131,7 @@ def remap_table_wp_to_master(cursor, table_name, wp_name, new_master_fid):
     mapping = []  # list of tuples (wp_fid, master_fid)
     sql = (
         f"""SELECT {pkey_column_escaped}, mapped.master_fid FROM {table_name_escaped} """
-        f"""LEFT JOIN {remap_table} AS mapped ON fid = mapped.wp_fid"""
+        f"""LEFT JOIN {remap_table} AS mapped ON {pkey_column_escaped} = mapped.wp_fid"""
     )
     for row in cursor.execute(sql):
         mapping.append((row[0], row[1]))
@@ -141,5 +141,6 @@ def remap_table_wp_to_master(cursor, table_name, wp_name, new_master_fid):
 
     for wp_fid, master_fid in mapping:
         cursor.execute(
-            f"""UPDATE {table_name_escaped} SET {pkey_column_escaped} = ? WHERE fid = ?""", (master_fid, -wp_fid)
+            f"""UPDATE {table_name_escaped} SET {pkey_column_escaped} = ? WHERE {pkey_column_escaped} = ?""",
+            (master_fid, -wp_fid),
         )
diff --git a/workpackages/wp.py b/workpackages/wp.py
index 627e4e0..6a48091 100644
--- a/workpackages/wp.py
+++ b/workpackages/wp.py
@@ -13,7 +13,7 @@
 import yaml
 
 from .wp_utils import escape_double_quotes
-from .remapping import remap_table_master_to_wp, remap_table_wp_to_master
+from .remapping import remap_table_master_to_wp, remap_table_wp_to_master, _table_pkey
 
 # Layout of files:
 #
@@ -191,7 +191,9 @@ def _logger_callback(level, text_bytes):
         for wp_table in wp_config.wp_tables:
             wp_table_name = wp_table.name
             wp_tab_name_esc = escape_double_quotes(wp_table_name)
-            c.execute(f"""SELECT max(fid) FROM {wp_tab_name_esc};""")
+            pkey_column = _table_pkey(c, wp_table_name)
+            pkey_column_escaped = escape_double_quotes(pkey_column)
+            c.execute(f"""SELECT max({pkey_column_escaped}) FROM {wp_tab_name_esc};""")
             new_master_fid = c.fetchone()[0]
             if new_master_fid is None:
                 new_master_fid = 1  # empty table so far