diff --git a/symbol.c b/symbol.c
index b9d41efda9..6512344441 100644
--- a/symbol.c
+++ b/symbol.c
@@ -24,9 +24,7 @@
 
 #define SYMBOL_PINNED_P(sym) (RSYMBOL(sym)->id&~ID_SCOPE_MASK)
 
-#define DYNAMIC_ID_P(id) (!(id&ID_STATIC_SYM)&&id>tLAST_OP_ID)
 #define STATIC_SYM2ID(sym) RSHIFT((unsigned long)(sym), RUBY_SPECIAL_SHIFT)
-#define STATIC_ID2SYM(id)  (((VALUE)(id)<<RUBY_SPECIAL_SHIFT)|SYMBOL_FLAG)
 
 static ID register_static_symid(ID, const char *, long, rb_encoding *);
 static ID register_static_symid_str(ID, VALUE);
@@ -748,6 +746,7 @@ rb_sym2id(VALUE sym)
     return id;
 }
 
+#undef rb_id2sym
 VALUE
 rb_id2sym(ID x)
 {
diff --git a/symbol.h b/symbol.h
index d624a46d20..3e14e02bdb 100644
--- a/symbol.h
+++ b/symbol.h
@@ -14,6 +14,15 @@
 
 #include "id.h"
 
+#define DYNAMIC_ID_P(id) (!(id&ID_STATIC_SYM)&&id>tLAST_OP_ID)
+#define STATIC_ID2SYM(id)  (((VALUE)(id)<<RUBY_SPECIAL_SHIFT)|SYMBOL_FLAG)
+
+#ifdef __GNUC__
+#define rb_id2sym(id) \
+    __extension__(__builtin_constant_p(id) && !DYNAMIC_ID_P(id) ? \
+		  STATIC_ID2SYM(id) : rb_id2sym(id))
+#endif
+
 struct RSymbol {
     struct RBasic basic;
     VALUE fstr;