diff --git a/src/cmd/acme/regx.c b/src/cmd/acme/regx.c
index 56ea900c..ec574563 100644
--- a/src/cmd/acme/regx.c
+++ b/src/cmd/acme/regx.c
@@ -15,6 +15,9 @@
 Rangeset	sel;
 Rune		*lastregexp;
 
+#undef class
+#define class regxclass /* some systems declare "class" in system headers */
+
 /*
  * Machine Information
  */