diff --git a/tcg/README b/tcg/README
index aa86992bca..9d1b100613 100644
--- a/tcg/README
+++ b/tcg/README
@@ -349,6 +349,9 @@ st32_i64 t0, t1, offset
 write(t0, t1 + offset)
 Write 8, 16, 32 or 64 bits to host memory.
 
+All this opcodes assume that the pointed host memory doesn't correspond
+to a global. In the latter case the behaviour is unpredictable.
+
 ********* 64-bit target on 32-bit host support
 
 The following opcodes are internal to TCG.  Thus they are to be implemented by
diff --git a/tcg/tcg-opc.h b/tcg/tcg-opc.h
index 2072281103..9651063414 100644
--- a/tcg/tcg-opc.h
+++ b/tcg/tcg-opc.h
@@ -57,9 +57,9 @@ DEF(ld8s_i32, 1, 1, 1, 0)
 DEF(ld16u_i32, 1, 1, 1, 0)
 DEF(ld16s_i32, 1, 1, 1, 0)
 DEF(ld_i32, 1, 1, 1, 0)
-DEF(st8_i32, 0, 2, 1, TCG_OPF_SIDE_EFFECTS)
-DEF(st16_i32, 0, 2, 1, TCG_OPF_SIDE_EFFECTS)
-DEF(st_i32, 0, 2, 1, TCG_OPF_SIDE_EFFECTS)
+DEF(st8_i32, 0, 2, 1, 0)
+DEF(st16_i32, 0, 2, 1, 0)
+DEF(st_i32, 0, 2, 1, 0)
 /* arith */
 DEF(add_i32, 1, 2, 0, 0)
 DEF(sub_i32, 1, 2, 0, 0)
@@ -115,10 +115,10 @@ DEF(ld16s_i64, 1, 1, 1, IMPL64)
 DEF(ld32u_i64, 1, 1, 1, IMPL64)
 DEF(ld32s_i64, 1, 1, 1, IMPL64)
 DEF(ld_i64, 1, 1, 1, IMPL64)
-DEF(st8_i64, 0, 2, 1, TCG_OPF_SIDE_EFFECTS | IMPL64)
-DEF(st16_i64, 0, 2, 1, TCG_OPF_SIDE_EFFECTS | IMPL64)
-DEF(st32_i64, 0, 2, 1, TCG_OPF_SIDE_EFFECTS | IMPL64)
-DEF(st_i64, 0, 2, 1, TCG_OPF_SIDE_EFFECTS | IMPL64)
+DEF(st8_i64, 0, 2, 1, IMPL64)
+DEF(st16_i64, 0, 2, 1, IMPL64)
+DEF(st32_i64, 0, 2, 1, IMPL64)
+DEF(st_i64, 0, 2, 1, IMPL64)
 /* arith */
 DEF(add_i64, 1, 2, 0, IMPL64)
 DEF(sub_i64, 1, 2, 0, IMPL64)