diff --git a/modules/libpref/public/prefapi.h b/modules/libpref/public/prefapi.h
index fa8f24d0be4..f9d9cc4f59f 100644
--- a/modules/libpref/public/prefapi.h
+++ b/modules/libpref/public/prefapi.h
@@ -30,7 +30,8 @@
 #include "jspubtd.h"
 
 #ifdef XP_WIN
-#ifndef NSPR20
+/* NSPR 1.0 compatibility */
+#ifdef NSPR
 #include "prhash.h"
 #else
 #include "plhash.h"