diff --git a/src/builtins/ppc/builtins-ppc.cc b/src/builtins/ppc/builtins-ppc.cc
index 9ada8ad44d..f089f086af 100644
--- a/src/builtins/ppc/builtins-ppc.cc
+++ b/src/builtins/ppc/builtins-ppc.cc
@@ -1101,11 +1101,17 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ PushStandardFrame(closure);
 
-  // Reset code age.
-  __ mov(r8, Operand(BytecodeArray::kNoAgeBytecodeAge));
-  __ StoreByte(r8, FieldMemOperand(kInterpreterBytecodeArrayRegister,
-                                   BytecodeArray::kBytecodeAgeOffset),
-               r0);
+  // Reset code age and the OSR arming. The OSR field and BytecodeAgeOffset are
+  // 8-bit fields next to each other, so we could just optimize by writing a
+  // 16-bit. These static asserts guard our assumption is valid.
+  STATIC_ASSERT(BytecodeArray::kBytecodeAgeOffset ==
+                BytecodeArray::kOSRNestingLevelOffset + kCharSize);
+  STATIC_ASSERT(BytecodeArray::kNoAgeBytecodeAge == 0);
+  __ li(r8, Operand(0));
+  __ StoreHalfWord(r8,
+                   FieldMemOperand(kInterpreterBytecodeArrayRegister,
+                                   BytecodeArray::kOSRNestingLevelOffset),
+                   r0);
 
   // Load initial bytecode offset.
   __ mov(kInterpreterBytecodeOffsetRegister,
diff --git a/src/builtins/s390/builtins-s390.cc b/src/builtins/s390/builtins-s390.cc
index 3134a3f43e..b242e8921a 100644
--- a/src/builtins/s390/builtins-s390.cc
+++ b/src/builtins/s390/builtins-s390.cc
@@ -1152,11 +1152,17 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ PushStandardFrame(closure);
 
-  // Reset code age.
-  __ mov(r1, Operand(BytecodeArray::kNoAgeBytecodeAge));
-  __ StoreByte(r1, FieldMemOperand(kInterpreterBytecodeArrayRegister,
-                                   BytecodeArray::kBytecodeAgeOffset),
-               r0);
+  // Reset code age and the OSR arming. The OSR field and BytecodeAgeOffset are
+  // 8-bit fields next to each other, so we could just optimize by writing a
+  // 16-bit. These static asserts guard our assumption is valid.
+  STATIC_ASSERT(BytecodeArray::kBytecodeAgeOffset ==
+                BytecodeArray::kOSRNestingLevelOffset + kCharSize);
+  STATIC_ASSERT(BytecodeArray::kNoAgeBytecodeAge == 0);
+  __ lghi(r1, Operand(0));
+  __ StoreHalfWord(r1,
+                   FieldMemOperand(kInterpreterBytecodeArrayRegister,
+                                   BytecodeArray::kOSRNestingLevelOffset),
+                   r0);
 
   // Load the initial bytecode offset.
   __ mov(kInterpreterBytecodeOffsetRegister,