diff --git a/vm_args.c b/vm_args.c
index fe7b7f0ca1..240835083a 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -187,6 +187,75 @@ args_rest_array(struct args_info *args)
     return ary;
 }
 
+static int
+keyword_hash_has_symbol_p_iter(st_data_t key, st_data_t val, st_data_t arg)
+{
+    if (SYMBOL_P((VALUE)key)) {
+        *(int*)arg |= 1;
+        return ST_STOP;
+    }
+
+    return ST_CONTINUE;
+}
+
+static int
+keyword_hash_has_symbol_p(VALUE kw_hash) {
+    int has_symbol = 0;
+    rb_hash_stlike_foreach(kw_hash, keyword_hash_has_symbol_p_iter, (st_data_t)(&has_symbol));
+    return has_symbol;
+}
+
+static int
+keyword_hash_p(VALUE *kw_hash_ptr, int check_symbol)
+{
+    *kw_hash_ptr = rb_check_hash_type(*kw_hash_ptr);
+
+    if (NIL_P(*kw_hash_ptr)) {
+        return FALSE;
+    }
+
+    if (!check_symbol || RHASH_EMPTY_P(*kw_hash_ptr) ||
+            keyword_hash_has_symbol_p(*kw_hash_ptr)) {
+        return TRUE;
+    }
+
+    *kw_hash_ptr = Qnil;
+    return FALSE;
+}
+
+static VALUE
+args_pop_keyword_hash(struct args_info *args, VALUE *kw_hash_ptr, int check_symbol)
+{
+    if (args->rest == Qfalse) {
+      from_argv:
+        VM_ASSERT(args->argc > 0);
+        *kw_hash_ptr = args->argv[args->argc-1];
+
+        if (keyword_hash_p(kw_hash_ptr, check_symbol)) {
+            args->argc--;
+            return TRUE;
+        }
+    }
+    else {
+        long len = RARRAY_LEN(args->rest);
+
+        if (len > 0) {
+            *kw_hash_ptr = RARRAY_AREF(args->rest, len - 1);
+
+            if (keyword_hash_p(kw_hash_ptr, check_symbol)) {
+                arg_rest_dup(args);
+                rb_ary_pop(args->rest);
+                return TRUE;
+            }
+        }
+        else {
+            goto from_argv;
+        }
+    }
+
+    return FALSE;
+}
+
 static int
 args_kw_argv_to_hash(struct args_info *args)
 {
@@ -452,6 +521,82 @@ ignore_keyword_hash_p(VALUE keyword_hash, const rb_iseq_t * const iseq, unsigned
            RHASH_EMPTY_P(keyword_hash);
 }
 
+VALUE rb_iseq_location(const rb_iseq_t *iseq);
+
+static st_table *caller_to_callees = 0;
+
+static VALUE
+rb_warn_check(const rb_execution_context_t * const ec, const rb_iseq_t *const iseq)
+{
+    if (!rb_warning_category_enabled_p(RB_WARN_CATEGORY_DEPRECATED)) return 1;
+
+    if (!iseq) return 0;
+
+    const st_data_t callee = (st_data_t)(iseq->body->iseq_unique_id * 2);
+
+    const rb_control_frame_t * const cfp = rb_vm_get_ruby_level_next_cfp(ec, ec->cfp);
+
+    if (!cfp) return 0;
+
+    const st_data_t caller = (st_data_t)cfp->pc;
+
+    if (!caller_to_callees) {
+        caller_to_callees = st_init_numtable();
+    }
+
+    st_data_t val;
+    if (st_lookup(caller_to_callees, caller, &val)) {
+        st_table *callees;
+
+        if (val & 1) {
+            val &= ~(st_data_t)1;
+            if (val == callee) return 1; /* already warned */
+
+            callees = st_init_numtable();
+            st_insert(callees, val, 1);
+        }
+        else {
+            callees = (st_table *) val;
+            if (st_is_member(callees, callee)) return 1; /* already warned */
+        }
+        st_insert(callees, callee, 1);
+        st_insert(caller_to_callees, caller, (st_data_t) callees);
+    }
+    else {
+        st_insert(caller_to_callees, caller, callee | 1);
+    }
+
+    return 0; /* not warned yet for the pair of caller and callee */
+}
+
+static inline void
+rb_warn_last_hash_to_keyword(rb_execution_context_t * const ec,
+                            struct rb_calling_info * const calling,
+                            const struct rb_callinfo *ci,
+                            const rb_iseq_t * const iseq)
+{
+    if (rb_warn_check(ec, iseq)) return;
+
+    VALUE name, loc;
+    name = rb_id2str(vm_ci_mid(ci));
+    loc = rb_iseq_location(iseq);
+    if (NIL_P(loc)) {
+        rb_warning("Using the last argument for `%"PRIsVALUE"' as keyword parameters is deprecated; maybe ** should be added to the call",
+                name);
+    }
+    else {
+        rb_warning("Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call");
+        if (calling->recv != Qundef) {
+            rb_compile_warning(RSTRING_PTR(RARRAY_AREF(loc, 0)), FIX2INT(RARRAY_AREF(loc, 1)),
+                            "The called method `%"PRIsVALUE"' is defined here", name);
+        }
+        else {
+            rb_compile_warning(RSTRING_PTR(RARRAY_AREF(loc, 0)), FIX2INT(RARRAY_AREF(loc, 1)),
+                            "The called method is defined here");
+        }
+    }
+}
+
 static int
 setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * const iseq,
 			 struct rb_calling_info *const calling,
@@ -626,6 +771,14 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
         }
     }
 
+    if (!kw_flag && args->kw_argv == NULL &&
+            (iseq->body->param.flags.has_kw || iseq->body->param.flags.has_kwrest) &&
+            given_argc > min_argc &&
+            args_pop_keyword_hash(args, &keyword_hash, !iseq->body->param.flags.has_kwrest)) {
+        rb_warn_last_hash_to_keyword(ec, calling, ci, iseq);
+        given_argc--;
+    }
+
     if (given_argc > max_argc && max_argc != UNLIMITED_ARGUMENTS) {
 	if (arg_setup_type == arg_setup_block) {
 	    /* truncate */