diff --git a/array.c b/array.c
index ae3cc49e26..e49071d5a1 100644
--- a/array.c
+++ b/array.c
@@ -4271,6 +4271,17 @@ ary_hash_orset(st_data_t *key, st_data_t *value, st_data_t arg, int existing)
     return ST_CONTINUE;
 }
 
+static void
+rb_ary_union(VALUE ary_union, VALUE ary)
+{
+    long i;
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+        VALUE elt = rb_ary_elt(ary, i);
+        if (rb_ary_includes_by_eql(ary_union, elt)) continue;
+        rb_ary_push(ary_union, elt);
+    }
+}
+
 /*
  *  call-seq:
  *     ary | other_ary     -> new_ary
@@ -4295,16 +4306,8 @@ rb_ary_or(VALUE ary1, VALUE ary2)
     ary2 = to_ary(ary2);
     if (RARRAY_LEN(ary1) + RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
 	ary3 = rb_ary_new();
-	for (i=0; i<RARRAY_LEN(ary1); i++) {
-	    VALUE elt = rb_ary_elt(ary1, i);
-	    if (rb_ary_includes_by_eql(ary3, elt)) continue;
-	    rb_ary_push(ary3, elt);
-	}
-	for (i=0; i<RARRAY_LEN(ary2); i++) {
-	    VALUE elt = rb_ary_elt(ary2, i);
-	    if (rb_ary_includes_by_eql(ary3, elt)) continue;
-	    rb_ary_push(ary3, elt);
-	}
+        rb_ary_union(ary3, ary1);
+        rb_ary_union(ary3, ary2);
 	return ary3;
     }
 
@@ -4353,21 +4356,9 @@ rb_ary_union_multi(int argc, VALUE *argv, VALUE ary)
     if (sum <= SMALL_ARRAY_LEN) {
         ary_union = rb_ary_new();
 
-        for (j = 0; j < RARRAY_LEN(ary); j++) {
-            VALUE elt = rb_ary_elt(ary, j);
-            if (rb_ary_includes_by_eql(ary_union, elt)) continue;
-            rb_ary_push(ary_union, elt);
-        }
+        rb_ary_union(ary_union, ary);
+        for (i = 0; i < argc; i++) rb_ary_union(ary_union, argv[i]);
 
-        for (i = 0; i < argc; i++) {
-            VALUE argv_i = argv[i];
-
-            for (j = 0; j < RARRAY_LEN(argv_i); j++) {
-                VALUE elt = rb_ary_elt(argv_i, j);
-                if (rb_ary_includes_by_eql(ary_union, elt)) continue;
-                rb_ary_push(ary_union, elt);
-            }
-        }
         return ary_union;
     }