diff --git a/js/src/jit/arm/CodeGenerator-arm.cpp b/js/src/jit/arm/CodeGenerator-arm.cpp
index f83ef021c259..e545f38707ae 100644
--- a/js/src/jit/arm/CodeGenerator-arm.cpp
+++ b/js/src/jit/arm/CodeGenerator-arm.cpp
@@ -3368,3 +3368,23 @@ CodeGeneratorARM::visitAsmJSPassStackArgI64(LAsmJSPassStackArgI64* ins)
     else
         masm.store64(ToRegister64(ins->arg()), dst);
 }
+
+void
+CodeGeneratorARM::visitAsmSelectI64(LAsmSelectI64* lir)
+{
+    Register cond = ToRegister(lir->condExpr());
+    const LInt64Allocation falseExpr = lir->falseExpr();
+
+    Register64 out = ToOutRegister64(lir);
+    MOZ_ASSERT(ToRegister64(lir->trueExpr()) == out, "true expr is reused for input");
+
+    masm.ma_cmp(cond, Imm32(0));
+    if (falseExpr.low().isRegister()) {
+        masm.ma_mov(ToRegister(falseExpr.low()), out.low, LeaveCC, Assembler::Equal);
+        masm.ma_mov(ToRegister(falseExpr.high()), out.high, LeaveCC, Assembler::Equal);
+    } else {
+        masm.ma_ldr(ToAddress(falseExpr.low()), out.low, Offset, Assembler::Equal);
+        masm.ma_ldr(ToAddress(falseExpr.high()), out.high, Offset, Assembler::Equal);
+    }
+}
+
diff --git a/js/src/jit/arm/CodeGenerator-arm.h b/js/src/jit/arm/CodeGenerator-arm.h
index 9554cfd6a379..192569b354b5 100644
--- a/js/src/jit/arm/CodeGenerator-arm.h
+++ b/js/src/jit/arm/CodeGenerator-arm.h
@@ -170,6 +170,7 @@ class CodeGeneratorARM : public CodeGeneratorShared
     virtual void visitBitOpI64(LBitOpI64* lir);
     virtual void visitRotateI64(LRotateI64* lir);
     virtual void visitAsmJSPassStackArgI64(LAsmJSPassStackArgI64* lir);
+    virtual void visitAsmSelectI64(LAsmSelectI64* lir);
 
     // Out of line visitors.
     void visitOutOfLineBailout(OutOfLineBailout* ool);
diff --git a/js/src/jit/arm/Lowering-arm.cpp b/js/src/jit/arm/Lowering-arm.cpp
index e63fdfefdd2e..2f707d49f668 100644
--- a/js/src/jit/arm/Lowering-arm.cpp
+++ b/js/src/jit/arm/Lowering-arm.cpp
@@ -511,7 +511,15 @@ LIRGeneratorARM::lowerUrshD(MUrsh* mir)
 void
 LIRGeneratorARM::visitAsmSelect(MAsmSelect* ins)
 {
-    MOZ_ASSERT(ins->type() != MIRType::Int64);
+    if (ins->type() == MIRType::Int64) {
+        auto* lir = new(alloc()) LAsmSelectI64(useInt64RegisterAtStart(ins->trueExpr()),
+                                               useInt64(ins->falseExpr()),
+                                               useRegister(ins->condExpr())
+                                              );
+
+        defineInt64ReuseInput(lir, ins, LAsmSelectI64::TrueExprIndex);
+        return;
+    }
 
     auto* lir = new(alloc()) LAsmSelect(useRegisterAtStart(ins->trueExpr()),
                                         useRegister(ins->falseExpr()),