diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index bb2ba8748a..cdbeb1a1c5 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2939,11 +2939,11 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   Representation representation = access.representation();
   if (representation.IsSmi() && SmiValuesAre32Bits() &&
       instr->hydrogen()->representation().IsInteger32()) {
-#ifdef DEBUG
-    Register scratch = kScratchRegister;
-    __ Load(scratch, FieldOperand(object, offset), representation);
-    __ AssertSmi(scratch);
-#endif
+    if (FLAG_debug_code) {
+      Register scratch = kScratchRegister;
+      __ Load(scratch, FieldOperand(object, offset), representation);
+      __ AssertSmi(scratch);
+    }
 
     // Read int value directly from upper half of the smi.
     STATIC_ASSERT(kSmiTag == 0);
@@ -3154,17 +3154,17 @@ void LCodeGen::DoLoadKeyedFixedArray(LLoadKeyed* instr) {
   if (representation.IsInteger32() && SmiValuesAre32Bits() &&
       hinstr->elements_kind() == FAST_SMI_ELEMENTS) {
     ASSERT(!requires_hole_check);
-#ifdef DEBUG
-    Register scratch = kScratchRegister;
-    __ Load(scratch,
-            BuildFastArrayOperand(instr->elements(),
-                                  key,
-                                  FAST_ELEMENTS,
-                                  offset,
-                                  instr->additional_index()),
-            Representation::Smi());
-    __ AssertSmi(scratch);
-#endif
+    if (FLAG_debug_code) {
+      Register scratch = kScratchRegister;
+      __ Load(scratch,
+              BuildFastArrayOperand(instr->elements(),
+                                    key,
+                                    FAST_ELEMENTS,
+                                    offset,
+                                    instr->additional_index()),
+              Representation::Smi());
+      __ AssertSmi(scratch);
+    }
     // Read int value directly from upper half of the smi.
     STATIC_ASSERT(kSmiTag == 0);
     ASSERT(kSmiTagSize + kSmiShiftSize == 32);
@@ -4078,11 +4078,11 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
   if (representation.IsSmi() && SmiValuesAre32Bits() &&
       hinstr->value()->representation().IsInteger32()) {
     ASSERT(hinstr->store_mode() == STORE_TO_INITIALIZED_ENTRY);
-#ifdef DEBUG
-    Register scratch = kScratchRegister;
-    __ Load(scratch, FieldOperand(write_register, offset), representation);
-    __ AssertSmi(scratch);
-#endif
+    if (FLAG_debug_code) {
+      Register scratch = kScratchRegister;
+      __ Load(scratch, FieldOperand(write_register, offset), representation);
+      __ AssertSmi(scratch);
+    }
     // Store int value directly to upper half of the smi.
     STATIC_ASSERT(kSmiTag == 0);
     ASSERT(kSmiTagSize + kSmiShiftSize == 32);
@@ -4301,17 +4301,17 @@ void LCodeGen::DoStoreKeyedFixedArray(LStoreKeyed* instr) {
   if (representation.IsInteger32() && SmiValuesAre32Bits()) {
     ASSERT(hinstr->store_mode() == STORE_TO_INITIALIZED_ENTRY);
     ASSERT(hinstr->elements_kind() == FAST_SMI_ELEMENTS);
-#ifdef DEBUG
-    Register scratch = kScratchRegister;
-    __ Load(scratch,
-            BuildFastArrayOperand(instr->elements(),
-                                  key,
-                                  FAST_ELEMENTS,
-                                  offset,
-                                  instr->additional_index()),
-            Representation::Smi());
-    __ AssertSmi(scratch);
-#endif
+    if (FLAG_debug_code) {
+      Register scratch = kScratchRegister;
+      __ Load(scratch,
+              BuildFastArrayOperand(instr->elements(),
+                                    key,
+                                    FAST_ELEMENTS,
+                                    offset,
+                                    instr->additional_index()),
+              Representation::Smi());
+      __ AssertSmi(scratch);
+    }
     // Store int value directly to upper half of the smi.
     STATIC_ASSERT(kSmiTag == 0);
     ASSERT(kSmiTagSize + kSmiShiftSize == 32);