diff --git a/ChangeLog b/ChangeLog
index ac74ba3bd2..3e1d4e9c8c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Oct 29 23:54:35 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (sym_to_proc), proc.c (rb_block_clear_env_self): clear
+	  caller's self which is useless, so that it can get collected.
+	  [Fixes GH-592]
+
 Thu Oct 29 23:30:20 2015  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* lib/ipaddr.rb, test/test_ipaddr.rb: Reject invalid address contained
diff --git a/internal.h b/internal.h
index fbd0e28e18..1e439913c7 100644
--- a/internal.h
+++ b/internal.h
@@ -630,6 +630,7 @@ void rb_gc_mark_symbols(int full_mark);
 VALUE rb_proc_location(VALUE self);
 st_index_t rb_hash_proc(st_index_t hash, VALUE proc);
 int rb_block_arity(void);
+VALUE rb_block_clear_env_self(VALUE proc);
 
 /* process.c */
 #define RB_MAX_GROUPS (65536)
diff --git a/proc.c b/proc.c
index a13452329d..1ee442a7f8 100644
--- a/proc.c
+++ b/proc.c
@@ -636,6 +636,17 @@ rb_block_lambda(void)
     return proc_new(rb_cProc, TRUE);
 }
 
+VALUE
+rb_block_clear_env_self(VALUE proc)
+{
+    rb_proc_t *po;
+    rb_env_t *env;
+    GetProcPtr(proc, po);
+    GetEnvPtr(po->envval, env);
+    env->env[0] = Qnil;
+    return proc;
+}
+
 VALUE
 rb_f_lambda(void)
 {
diff --git a/string.c b/string.c
index 859018e5c1..526f476deb 100644
--- a/string.c
+++ b/string.c
@@ -8540,6 +8540,7 @@ sym_to_proc(VALUE sym)
     }
     else {
 	proc = rb_proc_new(sym_call, (VALUE)id);
+	rb_block_clear_env_self(proc);
 	aryp[index] = sym;
 	aryp[index + 1] = proc;
 	return proc;
diff --git a/version.h b/version.h
index 75fcbf3133..eb424edf07 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.1.8"
 #define RUBY_RELEASE_DATE "2015-10-29"
-#define RUBY_PATCHLEVEL 411
+#define RUBY_PATCHLEVEL 412
 
 #define RUBY_RELEASE_YEAR 2015
 #define RUBY_RELEASE_MONTH 10