diff --git a/src/common/scope_exit.h b/src/common/scope_exit.h
index 1176a72..e2ce9b3 100644
--- a/src/common/scope_exit.h
+++ b/src/common/scope_exit.h
@@ -41,4 +41,5 @@ ScopeExitHelper<Func> ScopeExit(Func&& func) {
  * }
  * \endcode
  */
-#define SCOPE_EXIT(body) auto CONCAT2(scope_exit_helper_, __LINE__) = detail::ScopeExit([&]() body)
+#define SCOPE_EXIT(body)                                                                           \
+    auto CONCAT2(scope_exit_helper_, __LINE__) = ::detail::ScopeExit([&]() body)
diff --git a/src/core/importer.cpp b/src/core/importer.cpp
index e52528c..fe782cc 100644
--- a/src/core/importer.cpp
+++ b/src/core/importer.cpp
@@ -6,6 +6,7 @@
 #include "common/assert.h"
 #include "common/common_paths.h"
 #include "common/file_util.h"
+#include "common/scope_exit.h"
 #include "common/string_util.h"
 #include "core/data_container.h"
 #include "core/decryptor.h"
@@ -60,7 +61,6 @@ bool SDMCImporter::Init() {
     }
 
     decryptor = std::make_unique<SDMCDecryptor>(config.sdmc_path);
-    cia_builder = std::make_unique<CIABuilder>();
 
     // Load SDMC Title DB
     {
@@ -694,6 +694,15 @@ bool SDMCImporter::BuildCIA(CIABuildType type, const ContentSpecifier& specifier
         }
     }
 
+    {
+        std::lock_guard lock{cia_builder_mutex};
+        cia_builder = std::make_unique<CIABuilder>();
+    }
+    SCOPE_EXIT({
+        std::lock_guard lock{cia_builder_mutex};
+        cia_builder.reset(); // To release file handles, etc
+    });
+
     const bool ret = cia_builder->Init(type, destination, tmd, config,
                                        FileUtil::GetDirectoryTreeSize(physical_path), callback);
     if (!ret) {
@@ -752,7 +761,10 @@ bool SDMCImporter::BuildCIA(CIABuildType type, const ContentSpecifier& specifier
 }
 
 void SDMCImporter::AbortBuildCIA() {
-    cia_builder->Abort();
+    std::lock_guard lock{cia_builder_mutex};
+    if (cia_builder) {
+        cia_builder->Abort();
+    }
 }
 
 void SDMCImporter::ListTitle(std::vector<ContentSpecifier>& out) const {
diff --git a/src/core/importer.h b/src/core/importer.h
index ff5bd25..3fc308b 100644
--- a/src/core/importer.h
+++ b/src/core/importer.h
@@ -6,6 +6,7 @@
 
 #include <functional>
 #include <memory>
+#include <mutex>
 #include <string>
 #include <vector>
 #include "common/common_types.h"
@@ -199,7 +200,9 @@ private:
     bool is_good{};
     Config config;
     std::unique_ptr<SDMCDecryptor> decryptor;
+
     std::unique_ptr<CIABuilder> cia_builder;
+    std::mutex cia_builder_mutex;
 
     // The NCCH used to dump CXIs.
     std::unique_ptr<NCCHContainer> dump_cxi_ncch;
diff --git a/src/core/ncch/cia_builder.cpp b/src/core/ncch/cia_builder.cpp
index d28f4a5..f0ea10f 100644
--- a/src/core/ncch/cia_builder.cpp
+++ b/src/core/ncch/cia_builder.cpp
@@ -67,7 +67,6 @@ bool CIABuilder::Init(CIABuildType type_, const std::string& destination, TitleM
     file = std::make_shared<HashedFile>(destination, "wb");
     if (!*file) {
         LOG_ERROR(Core, "Could not open file {}", destination);
-        file.reset();
         return false;
     }
 
@@ -82,7 +81,6 @@ bool CIABuilder::Init(CIABuildType type_, const std::string& destination, TitleM
         // Check for legit TMD
         if (!tmd.VerifyHashes() || !tmd.ValidateSignature()) {
             LOG_ERROR(Core, "TMD is not legit");
-            file.reset();
             return false;
         }
     }
@@ -95,14 +93,12 @@ bool CIABuilder::Init(CIABuildType type_, const std::string& destination, TitleM
     header.cert_size = CIA_CERT_SIZE;
     if (!WriteCert(config.certs_db_path)) {
         LOG_ERROR(Core, "Could not write cert to file {}", destination);
-        file.reset();
         return false;
     }
 
     // Ticket
     ticket_offset = Common::AlignUp(cert_offset + header.cert_size, CIA_ALIGNMENT);
     if (!WriteTicket(config.ticket_db_path, config.enc_title_keys_bin_path)) {
-        file.reset();
         return false;
     }
 
@@ -219,7 +215,6 @@ bool CIABuilder::WriteTicket(const std::string& ticket_db_path,
     file->Seek(ticket_offset, SEEK_SET);
     if (!ticket.Save(*file)) {
         LOG_ERROR(Core, "Could not write ticket");
-        file.reset();
         return false;
     }
     return true;
@@ -273,7 +268,6 @@ bool CIABuilder::AddContent(u16 content_id, NCCHContainer& ncch) {
         }
 
         if (ret != ResultStatus::Success) {
-            file.reset();
             return false;
         }
         file->GetHash(tmd_chunk.hash.data());
@@ -300,7 +294,6 @@ bool CIABuilder::AddContent(u16 content_id, NCCHContainer& ncch) {
         if (!decryptor.CryptAndWriteFile(ncch.file, ncch.file->GetSize(), file,
                                          progress_callback)) {
 
-            file.reset();
             return false;
         }
 
@@ -314,7 +307,6 @@ bool CIABuilder::AddContent(u16 content_id, NCCHContainer& ncch) {
         }
         if (!verified) {
             LOG_ERROR(Core, "Hash dismatch for content {}", content_id);
-            file.reset();
             return false;
         }
     }
@@ -355,7 +347,6 @@ bool CIABuilder::Finalize() {
     file->Seek(0, SEEK_SET);
     if (file->WriteBytes(&header, sizeof(header)) != sizeof(header)) {
         LOG_ERROR(Core, "Failed to write header");
-        file.reset();
         return false;
     }
 
@@ -365,7 +356,6 @@ bool CIABuilder::Finalize() {
     }
     file->Seek(tmd_offset, SEEK_SET);
     if (tmd.Save(*file) != ResultStatus::Success) {
-        file.reset();
         return false;
     }
 
@@ -374,13 +364,11 @@ bool CIABuilder::Finalize() {
         file->Seek(written, SEEK_SET);
         if (file->WriteBytes(&meta, sizeof(meta)) != sizeof(meta)) {
             LOG_ERROR(Core, "Failed to write meta");
-            file.reset();
             return false;
         }
     }
 
     callback(total_size, total_size);
-    file.reset();
     return true;
 }