diff --git a/ruby.c b/ruby.c
index ebc8f7224e..8287869d20 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1798,7 +1798,7 @@ copy_str(VALUE str, rb_encoding *enc, bool intern)
     return rb_enc_interned_str(RSTRING_PTR(str), RSTRING_LEN(str), enc);
 }
 
-#ifdef USE_YJIT
+#if USE_YJIT
 // Check that an environment variable is set to a truthy value
 static bool
 env_var_truthy(const char *name)