diff --git a/js/src/nanojit/LIR.h b/js/src/nanojit/LIR.h
index c2c3712e888c..dbe4d56aa0f6 100644
--- a/js/src/nanojit/LIR.h
+++ b/js/src/nanojit/LIR.h
@@ -145,8 +145,8 @@ namespace nanojit
         LIR_ldf     = LIR_ldd,
         LIR_ld32f   = LIR_lds2d,
 
-        // LIR_stb
-        LIR_sts     = LIR_stw,
+        LIR_stb     = LIR_stl2b,
+        LIR_sts     = LIR_stl2w,
         LIR_sti     = LIR_stl,
 #ifdef NANOJIT_64BIT
         LIR_stqi    = LIR_stq,
diff --git a/js/src/nanojit/LIRopcode.tbl b/js/src/nanojit/LIRopcode.tbl
index 6528e7acf9f8..0629db01c309 100644
--- a/js/src/nanojit/LIRopcode.tbl
+++ b/js/src/nanojit/LIRopcode.tbl
@@ -152,8 +152,8 @@ OP_64(ldq,      22, Ld,   I64, -1)  // load quad
 OP___(ldd,      23, Ld,   F64, -1)  // load double
 OP___(lds2d,    24, Ld,   F64, -1)  // load single and extend to a double
 
-OP___(stb,      25, Sti,  Void, 0)  // store byte
-OP___(stw,      26, Sti,  Void, 0)  // store word
+OP___(stl2b,    25, Sti,  Void, 0)  // store long truncated to byte
+OP___(stl2w,    26, Sti,  Void, 0)  // store long truncated to word
 OP___(stl,      27, Sti,  Void, 0)  // store long
 OP_64(stq,      28, Sti,  Void, 0)  // store quad
 OP___(std,      29, Sti,  Void, 0)  // store double