--- a/js/src/jit/MacroAssembler.cpp
+++ b/js/src/jit/MacroAssembler.cpp
@@ -2769,26 +2769,32 @@ MacroAssembler::callWithABINoProfiler(vo
 }
 
 void
 MacroAssembler::callWithABI(wasm::BytecodeOffset callOffset, wasm::SymbolicAddress imm,
                             MoveOp::Type result)
 {
     MOZ_ASSERT(wasm::NeedsBuiltinThunk(imm));
 
+    // We clobber WasmTlsReg below in the loadWasmTlsRegFromFrame(), but Ion
+    // assumes it is non-volatile, so preserve it manually.
+    Push(WasmTlsReg);
+
     uint32_t stackAdjust;
     callWithABIPre(&stackAdjust, /* callFromWasm = */ true);
 
     // The TLS register is used in builtin thunks and must be set, by ABI:
     // reload it after passing arguments, which might have used it at spill
     // points when placing arguments.
     loadWasmTlsRegFromFrame();
 
     call(wasm::CallSiteDesc(callOffset.bytecodeOffset, wasm::CallSite::Symbolic), imm);
     callWithABIPost(stackAdjust, result, /* callFromWasm = */ true);
+
+    Pop(WasmTlsReg);
 }
 
 // ===============================================================
 // Exit frame footer.
 
 void
 MacroAssembler::linkExitFrame(Register cxreg)
 {