diff --git a/string.c b/string.c
index 267efd407c..7f9559cb83 100644
--- a/string.c
+++ b/string.c
@@ -4630,7 +4630,7 @@ rb_str_include_range_p(VALUE beg, VALUE end, VALUE val, VALUE exclusive)
 
 		if (ISASCII(b) && ISASCII(e) && ISASCII(v)) {
 		    if (b <= v && v < e) return Qtrue;
-            return RBOOL(!RTEST(exclusive) && v == e);
+		    return RBOOL(!RTEST(exclusive) && v == e);
 		}
 	    }
 	}