diff --git a/Makefile b/Makefile
index 761092f09d24020bffa1937d081eb79ca2ee1f3c..8a8c5ac0f3c63c990f5127900c86e6e9cd207951 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ endif
 
 all: crystal
 spec: all_spec
-	CRYSTAL_BIN="$(O)/all_spec" crystal
+	$(O)/all_spec
 
 crystal: $(O)/crystal
 all_spec: $(O)/all_spec