diff --git a/js/src/jit-test/tests/wasm/regress/bug1953381.js b/js/src/jit-test/tests/wasm/regress/bug1953381.js
new file mode 100644
index 000000000000..3fa1a3f32a9c
--- /dev/null
+++ b/js/src/jit-test/tests/wasm/regress/bug1953381.js
@@ -0,0 +1,32 @@
+// |jit-test| skip-if: !wasmSimdEnabled()
+
+for (let [mask, exp] of [
+    [0xFF000000, 0x12bcdef0], // optimized to PBLENDVB on x86
+    [0x00FFFFFF, 0x9a345678], // optimized to PBLENDVB on x86
+    [0xFFFF0000, 0x1234def0], // optimized to PBLENDW on x86
+    [0x0000FFFF, 0x9abc5678], // optimized to PBLENDW on x86
+    [0x10000000, 0x9abcdef0], // non-optimizable mask
+    [0x9FFFFFFF, 0x12345678], // non-optimizable mask
+    [0x00000000, 0x9abcdef0],
+    [0xFFFFFFFF, 0x12345678],
+]) {
+    const ins = wasmEvalText(`(module
+        (memory (export "memory") 1 1)
+        (func (export "test")
+          i32.const 48
+          i32.const 0
+          v128.load
+          i32.const 16
+          v128.load
+          v128.const i32x4 ${mask} ${mask} ${mask} ${mask}
+          v128.bitselect
+          v128.store
+        )
+        (data (i32.const 0)  "\\78\\56\\34\\12\\78\\56\\34\\12\\78\\56\\34\\12\\78\\56\\34\\12")
+        (data (i32.const 16) "\\f0\\de\\bc\\9a\\f0\\de\\bc\\9a\\f0\\de\\bc\\9a\\f0\\de\\bc\\9a")
+    )`);
+    ins.exports.test();
+    var result = new DataView(ins.exports.memory.buffer).getUint32(48, true);
+    var expected = exp >>> 0;
+    assertEq(result, expected);
+}
diff --git a/js/src/jit-test/tests/wasm/simd/bitselect-x64-ion-codegen.js b/js/src/jit-test/tests/wasm/simd/bitselect-x64-ion-codegen.js
index 6d2a105d12a8..80ebffcdf83f 100644
--- a/js/src/jit-test/tests/wasm/simd/bitselect-x64-ion-codegen.js
+++ b/js/src/jit-test/tests/wasm/simd/bitselect-x64-ion-codegen.js
@@ -29,7 +29,7 @@ codegenTestX64_adhoc(
       (func (export "f") (param v128) (param v128) (param v128) (result v128)
         (v128.bitselect (local.get 0) (local.get 1) (v128.const i32x4 -1 0 0 -1))))`,
       'f',
-  `66 0f 3a 0e c1 c3         pblendw \\$0xC3, %xmm1, %xmm0`);
+  `66 0f 3a 0e c1 3c         pblendw \\$0x3C, %xmm1, %xmm0`);
 
 // vpblendvp optimization when bitselect follows comparison.
 // Non-AVX pblendvb uses xmm0 as an implicit read-only operand.
diff --git a/js/src/jit/x86-shared/Lowering-x86-shared.cpp b/js/src/jit/x86-shared/Lowering-x86-shared.cpp
index e9786d4882cb..2137d8f03b7e 100644
--- a/js/src/jit/x86-shared/Lowering-x86-shared.cpp
+++ b/js/src/jit/x86-shared/Lowering-x86-shared.cpp
@@ -1161,9 +1161,9 @@ bool MWasmTernarySimd128::specializeBitselectConstantMaskAsShuffle(
   const SimdConstant::I8x16& bytes = constant.asInt8x16();
   for (int8_t i = 0; i < 16; i++) {
     if (bytes[i] == -1) {
-      shuffle[i] = i + 16;
-    } else if (bytes[i] == 0) {
       shuffle[i] = i;
+    } else if (bytes[i] == 0) {
+      shuffle[i] = i + 16;
     } else {
       return false;
     }