diff --git a/src/worksp/gc2/make.ss b/src/worksp/gc2/make.ss
index a6f2ae413b..f0d629dbbc 100644
--- a/src/worksp/gc2/make.ss
+++ b/src/worksp/gc2/make.ss
@@ -178,7 +178,7 @@
 	  "/D GC2_AS_EXPORT "
 	  (if accounting-gc?
 	      "/D NEWGC_BTC_ACCOUNT "
-	      "/D USE_COMPACT_3M_GC")
+	      "/D USE_COMPACT_3M_GC ")
 	  mz-inc))
 (compile "../../mzscheme/src/mzsj86.c" "xsrc/mzsj86.obj" '() mz-inc)