diff --git a/driver/main.cpp b/driver/main.cpp
index cd13144..2f62443 100644
--- a/driver/main.cpp
+++ b/driver/main.cpp
@@ -96,7 +96,7 @@ int main(int argc, char* argv[])
       return 1;
     }
 
-    if (nod::DiscBuilderGCN::CalculateTotalSizeRequired(argv[2]) == UINT64_MAX)
+    if (!nod::DiscBuilderGCN::CalculateTotalSizeRequired(argv[2]))
       return 1;
 
     nod::EBuildResult ret;
@@ -123,7 +123,7 @@ int main(int argc, char* argv[])
     }
 
     bool dual = false;
-    if (nod::DiscBuilderWii::CalculateTotalSizeRequired(argv[2], dual) == UINT64_MAX)
+    if (!nod::DiscBuilderWii::CalculateTotalSizeRequired(argv[2], dual))
       return 1;
 
     nod::EBuildResult ret;
@@ -164,7 +164,7 @@ int main(int argc, char* argv[])
       return 1;
     }
 
-    if (nod::DiscMergerGCN::CalculateTotalSizeRequired(static_cast<nod::DiscGCN&>(*disc), argv[2]) == UINT64_MAX)
+    if (!nod::DiscMergerGCN::CalculateTotalSizeRequired(static_cast<nod::DiscGCN&>(*disc), argv[2]))
       return 1;
 
     nod::EBuildResult ret;
@@ -206,7 +206,7 @@ int main(int argc, char* argv[])
     }
 
     bool dual = false;
-    if (nod::DiscMergerWii::CalculateTotalSizeRequired(static_cast<nod::DiscWii&>(*disc), argv[2], dual) == UINT64_MAX)
+    if (!nod::DiscMergerWii::CalculateTotalSizeRequired(static_cast<nod::DiscWii&>(*disc), argv[2], dual))
       return 1;
 
     nod::EBuildResult ret;
diff --git a/include/nod/DiscBase.hpp b/include/nod/DiscBase.hpp
index b666f25..7503881 100644
--- a/include/nod/DiscBase.hpp
+++ b/include/nod/DiscBase.hpp
@@ -5,6 +5,7 @@
 #include <cstring>
 #include <functional>
 #include <memory>
+#include <optional>
 #include <string>
 #include <unordered_map>
 #include <vector>
@@ -425,9 +426,9 @@ public:
     : m_parent(parent), m_kind(kind), m_isWii(isWii) {}
     virtual std::unique_ptr<IPartWriteStream> beginWriteStream(uint64_t offset) = 0;
     bool buildFromDirectory(IPartWriteStream& ws, SystemStringView dirIn);
-    static uint64_t CalculateTotalSizeBuild(SystemStringView dirIn, PartitionKind kind, bool isWii);
+    static std::optional<uint64_t> CalculateTotalSizeBuild(SystemStringView dirIn, PartitionKind kind, bool isWii);
     bool mergeFromDirectory(IPartWriteStream& ws, const IPartition* partIn, SystemStringView dirIn);
-    static uint64_t CalculateTotalSizeMerge(const IPartition* partIn, SystemStringView dirIn);
+    static std::optional<uint64_t> CalculateTotalSizeMerge(const IPartition* partIn, SystemStringView dirIn);
   };
 
 protected:
diff --git a/include/nod/DiscGCN.hpp b/include/nod/DiscGCN.hpp
index 040070c..a16b897 100644
--- a/include/nod/DiscGCN.hpp
+++ b/include/nod/DiscGCN.hpp
@@ -20,7 +20,7 @@ class DiscBuilderGCN : public DiscBuilderBase {
 public:
   DiscBuilderGCN(SystemStringView outPath, FProgress progressCB);
   EBuildResult buildFromDirectory(SystemStringView dirIn);
-  static uint64_t CalculateTotalSizeRequired(SystemStringView dirIn);
+  static std::optional<uint64_t> CalculateTotalSizeRequired(SystemStringView dirIn);
 };
 
 class DiscMergerGCN {
@@ -30,7 +30,7 @@ class DiscMergerGCN {
 public:
   DiscMergerGCN(SystemStringView outPath, DiscGCN& sourceDisc, FProgress progressCB);
   EBuildResult mergeFromDirectory(SystemStringView dirIn);
-  static uint64_t CalculateTotalSizeRequired(DiscGCN& sourceDisc, SystemStringView dirIn);
+  static std::optional<uint64_t> CalculateTotalSizeRequired(DiscGCN& sourceDisc, SystemStringView dirIn);
 };
 
 } // namespace nod
diff --git a/include/nod/DiscWii.hpp b/include/nod/DiscWii.hpp
index 8ef8d5a..ee9abc4 100644
--- a/include/nod/DiscWii.hpp
+++ b/include/nod/DiscWii.hpp
@@ -16,7 +16,7 @@ class DiscBuilderWii : public DiscBuilderBase {
 public:
   DiscBuilderWii(SystemStringView outPath, bool dualLayer, FProgress progressCB);
   EBuildResult buildFromDirectory(SystemStringView dirIn);
-  static uint64_t CalculateTotalSizeRequired(SystemStringView dirIn, bool& dualLayer);
+  static std::optional<uint64_t> CalculateTotalSizeRequired(SystemStringView dirIn, bool& dualLayer);
 };
 
 class DiscMergerWii {
@@ -26,7 +26,7 @@ class DiscMergerWii {
 public:
   DiscMergerWii(SystemStringView outPath, DiscWii& sourceDisc, bool dualLayer, FProgress progressCB);
   EBuildResult mergeFromDirectory(SystemStringView dirIn);
-  static uint64_t CalculateTotalSizeRequired(DiscWii& sourceDisc, SystemStringView dirIn, bool& dualLayer);
+  static std::optional<uint64_t> CalculateTotalSizeRequired(DiscWii& sourceDisc, SystemStringView dirIn, bool& dualLayer);
 };
 
 } // namespace nod
diff --git a/lib/DiscBase.cpp b/lib/DiscBase.cpp
index 296015d..75e5c3b 100644
--- a/lib/DiscBase.cpp
+++ b/lib/DiscBase.cpp
@@ -769,8 +769,8 @@ bool DiscBuilderBase::PartitionBuilderBase::buildFromDirectory(IPartWriteStream&
   return true;
 }
 
-uint64_t DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(SystemStringView dirIn, PartitionKind kind,
-                                                                        bool isWii) {
+std::optional<uint64_t> DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(SystemStringView dirIn,
+                                                                                       PartitionKind kind, bool isWii) {
   SystemString dirStr(dirIn);
   SystemString basePath = isWii ? dirStr + _SYS_STR("/") + getKindString(kind) : dirStr;
   SystemString dolIn = basePath + _SYS_STR("/sys/main.dol");
@@ -779,11 +779,11 @@ uint64_t DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(SystemSt
   Sstat dolStat;
   if (Stat(dolIn.c_str(), &dolStat)) {
     LogModule.report(logvisor::Error, fmt(_SYS_STR("unable to stat {}")), dolIn);
-    return UINT64_MAX;
+    return std::nullopt;
   }
   uint64_t totalSz = ROUND_UP_32(dolStat.st_size);
   if (!RecursiveCalculateTotalSize(totalSz, nullptr, filesIn.c_str()))
-    return UINT64_MAX;
+    return std::nullopt;
   return totalSz;
 }
 
@@ -843,15 +843,15 @@ bool DiscBuilderBase::PartitionBuilderBase::mergeFromDirectory(IPartWriteStream&
   return true;
 }
 
-uint64_t DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(const IPartition* partIn,
-                                                                        SystemStringView dirIn) {
+std::optional<uint64_t> DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(const IPartition* partIn,
+                                                                                       SystemStringView dirIn) {
   SystemString dirStr(dirIn);
   SystemString basePath = partIn->isWii() ? dirStr + _SYS_STR("/") + getKindString(partIn->getKind()) : dirStr;
   SystemString filesIn = basePath + _SYS_STR("/files");
 
   uint64_t totalSz = ROUND_UP_32(partIn->getDOLSize());
   if (!RecursiveCalculateTotalSize(totalSz, &partIn->getFSTRoot(), filesIn.c_str()))
-    return UINT64_MAX;
+    return std::nullopt;
   return totalSz;
 }
 
diff --git a/lib/DiscGCN.cpp b/lib/DiscGCN.cpp
index ebe0dbc..22bd82d 100644
--- a/lib/DiscGCN.cpp
+++ b/lib/DiscGCN.cpp
@@ -372,14 +372,14 @@ EBuildResult DiscBuilderGCN::buildFromDirectory(SystemStringView dirIn) {
   return pb.buildFromDirectory(dirIn) ? EBuildResult::Success : EBuildResult::Failed;
 }
 
-uint64_t DiscBuilderGCN::CalculateTotalSizeRequired(SystemStringView dirIn) {
-  uint64_t sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(dirIn, PartitionKind::Data, false);
-  if (sz == UINT64_MAX)
-    return UINT64_MAX;
-  sz += 0x30000;
+std::optional<uint64_t> DiscBuilderGCN::CalculateTotalSizeRequired(SystemStringView dirIn) {
+  std::optional<uint64_t> sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(dirIn, PartitionKind::Data, false);
+  if (!sz)
+    return sz;
+  *sz += 0x30000;
   if (sz > 0x57058000) {
-    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), sz, 0x57058000);
-    return UINT64_MAX;
+    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), *sz, 0x57058000);
+    return std::nullopt;
   }
   return sz;
 }
@@ -416,14 +416,14 @@ EBuildResult DiscMergerGCN::mergeFromDirectory(SystemStringView dirIn) {
              : EBuildResult::Failed;
 }
 
-uint64_t DiscMergerGCN::CalculateTotalSizeRequired(DiscGCN& sourceDisc, SystemStringView dirIn) {
-  uint64_t sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(sourceDisc.getDataPartition(), dirIn);
-  if (sz == UINT64_MAX)
-    return UINT64_MAX;
-  sz += 0x30000;
+std::optional<uint64_t> DiscMergerGCN::CalculateTotalSizeRequired(DiscGCN& sourceDisc, SystemStringView dirIn) {
+  std::optional<uint64_t> sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(sourceDisc.getDataPartition(), dirIn);
+  if (!sz)
+    return std::nullopt;
+  *sz += 0x30000;
   if (sz > 0x57058000) {
-    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), sz, 0x57058000);
-    return -1;
+    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), *sz, 0x57058000);
+    return std::nullopt;
   }
   return sz;
 }
diff --git a/lib/DiscWii.cpp b/lib/DiscWii.cpp
index 0bf17ef..0b525b8 100644
--- a/lib/DiscWii.cpp
+++ b/lib/DiscWii.cpp
@@ -1229,19 +1229,19 @@ EBuildResult DiscBuilderWii::buildFromDirectory(SystemStringView dirIn) {
   return EBuildResult::Success;
 }
 
-uint64_t DiscBuilderWii::CalculateTotalSizeRequired(SystemStringView dirIn, bool& dualLayer) {
-  uint64_t sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(dirIn, PartitionKind::Data, true);
-  if (sz == UINT64_MAX)
-    return UINT64_MAX;
-  auto szDiv = std::lldiv(sz, 0x1F0000);
+std::optional<uint64_t> DiscBuilderWii::CalculateTotalSizeRequired(SystemStringView dirIn, bool& dualLayer) {
+  std::optional<uint64_t> sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeBuild(dirIn, PartitionKind::Data, true);
+  if (!sz)
+    return sz;  
+  auto szDiv = std::lldiv(*sz, 0x1F0000);
   if (szDiv.rem)
     ++szDiv.quot;
   sz = szDiv.quot * 0x200000;
-  sz += 0x200000;
+  *sz += 0x200000;
   dualLayer = (sz > 0x118240000);
   if (sz > 0x1FB4E0000) {
-    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), sz, 0x1FB4E0000);
-    return UINT64_MAX;
+    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), *sz, 0x1FB4E0000);
+    return std::nullopt;
   }
   return sz;
 }
@@ -1336,19 +1336,19 @@ EBuildResult DiscMergerWii::mergeFromDirectory(SystemStringView dirIn) {
   return EBuildResult::Success;
 }
 
-uint64_t DiscMergerWii::CalculateTotalSizeRequired(DiscWii& sourceDisc, SystemStringView dirIn, bool& dualLayer) {
-  uint64_t sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(sourceDisc.getDataPartition(), dirIn);
-  if (sz == UINT64_MAX)
-    return UINT64_MAX;
-  auto szDiv = std::lldiv(sz, 0x1F0000);
+std::optional<uint64_t> DiscMergerWii::CalculateTotalSizeRequired(DiscWii& sourceDisc, SystemStringView dirIn, bool& dualLayer) {
+  std::optional<uint64_t> sz = DiscBuilderBase::PartitionBuilderBase::CalculateTotalSizeMerge(sourceDisc.getDataPartition(), dirIn);
+  if (!sz)
+    return std::nullopt;
+  auto szDiv = std::lldiv(*sz, 0x1F0000);
   if (szDiv.rem)
     ++szDiv.quot;
   sz = szDiv.quot * 0x200000;
-  sz += 0x200000;
+  *sz += 0x200000;
   dualLayer = (sz > 0x118240000);
   if (sz > 0x1FB4E0000) {
-    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), sz, 0x1FB4E0000);
-    return UINT64_MAX;
+    LogModule.report(logvisor::Error, fmt(_SYS_STR("disc capacity exceeded [{} / {}]")), *sz, 0x1FB4E0000);
+    return std::nullopt;
   }
   return sz;
 }