diff --git a/basis/environment/winnt/winnt.factor b/basis/environment/winnt/winnt.factor
index eb90a36ee7..afe4425b3f 100644
--- a/basis/environment/winnt/winnt.factor
+++ b/basis/environment/winnt/winnt.factor
@@ -6,6 +6,8 @@ alien.c-types sequences windows.errors io.streams.memory
 io.encodings io ;
 IN: environment.winnt
 
+<< "TCHAR" require-c-arrays >>
+
 M: winnt os-env ( key -- value )
     MAX_UNICODE_PATH "TCHAR" <c-array>
     [ dup length GetEnvironmentVariable ] keep over 0 = [