diff --git a/1.9/plink_common.h b/1.9/plink_common.h
index 8a053276..6a03b822 100644
--- a/1.9/plink_common.h
+++ b/1.9/plink_common.h
@@ -43,7 +43,7 @@
 
 // Uncomment this to prevent all unstable features from being accessible from
 // the command line.
-#define STABLE_BUILD
+// #define STABLE_BUILD
 
 #define SPECIES_HUMAN 0
 #define SPECIES_COW 1