diff --git a/dlls/ntdll/directory.c b/dlls/ntdll/directory.c
index be55a5a8c1..db1e086467 100644
--- a/dlls/ntdll/directory.c
+++ b/dlls/ntdll/directory.c
@@ -2674,6 +2674,14 @@ NTSTATUS nt_to_unix_file_name_attr( const OBJECT_ATTRIBUTES *attr, ANSI_STRING *
     NTSTATUS status;
     BOOLEAN check_case = !(attr->Attributes & OBJ_CASE_INSENSITIVE);
 
+    const char *sgi = getenv("SteamGameId");
+    if (sgi && !strcmp(sgi, "703080")) {
+        TRACE("Forcing case-insensitivity for Planet Zoo\n");
+        BOOLEAN check_case = 0;
+    } else {
+        BOOLEAN check_case = !(attr->Attributes & OBJ_CASE_INSENSITIVE);
+    }
+
     if (!attr->RootDirectory)  /* without root dir fall back to normal lookup */
         return wine_nt_to_unix_file_name( attr->ObjectName, unix_name_ret, disposition, check_case );
 
diff --git a/dlls/ntdll/file.c b/dlls/ntdll/file.c
index a9770290e0..de23419c5c 100644
--- a/dlls/ntdll/file.c
+++ b/dlls/ntdll/file.c
@@ -214,6 +214,12 @@ static NTSTATUS FILE_CreateFile( PHANDLE handle, ACCESS_MASK access, POBJECT_ATT
 
     if (alloc_size) FIXME( "alloc_size not supported\n" );
 
+    const char *sgi = getenv("SteamGameId");
+    if (sgi && !strcmp(sgi, "703080")) {
+        TRACE("Forcing case-insensitive lookup for Planet Zoo\n");
+        attr->Attributes |= OBJ_CASE_INSENSITIVE;
+    }
+
     if (options & FILE_OPEN_BY_FILE_ID)
         io->u.Status = file_id_to_unix_file_name( attr, &unix_name );
     else