diff --git a/dom/xhr/XMLHttpRequestMainThread.cpp b/dom/xhr/XMLHttpRequestMainThread.cpp
index 59352f1e716..e9472466d26 100644
--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -4182,7 +4182,7 @@ nsresult ArrayBufferBuilder::MapToFileInPackage(const nsCString& aFile,
   if (!zip) {
     return NS_ERROR_FAILURE;
   }
-  nsZipItem* zipItem = zip->GetItem(aFile.get());
+  nsZipItem* zipItem = zip->GetItem(aFile);
   if (!zipItem) {
     return NS_ERROR_FILE_NOT_FOUND;
   }
diff --git a/gfx/thebes/gfxFT2FontList.cpp b/gfx/thebes/gfxFT2FontList.cpp
index 5c94e81d9be..13a32ef76fd 100644
--- a/gfx/thebes/gfxFT2FontList.cpp
+++ b/gfx/thebes/gfxFT2FontList.cpp
@@ -103,7 +103,7 @@ already_AddRefed<SharedFTFace> FT2FontEntry::GetFTFace(bool aCommit) {
   RefPtr<SharedFTFace> face;
   if (mFilename[0] != '/') {
     RefPtr<nsZipArchive> reader = Omnijar::GetReader(Omnijar::Type::GRE);
-    nsZipItem* item = reader->GetItem(mFilename.get());
+    nsZipItem* item = reader->GetItem(mFilename);
     NS_ASSERTION(item, "failed to find zip entry");
 
     uint32_t bufSize = item->RealSize();
@@ -468,7 +468,7 @@ hb_face_t* FT2FontEntry::CreateHBFace() const {
     // A relative path means an omnijar resource, which we may need to
     // decompress to a temporary buffer.
     RefPtr<nsZipArchive> reader = Omnijar::GetReader(Omnijar::Type::GRE);
-    nsZipItem* item = reader->GetItem(mFilename.get());
+    nsZipItem* item = reader->GetItem(mFilename);
     MOZ_ASSERT(item, "failed to find zip entry");
     if (item) {
       // TODO(jfkthame):
@@ -1510,7 +1510,7 @@ void gfxFT2FontList::AppendFacesFromOmnijarEntry(nsZipArchive* aArchive,
     }
   }
 
-  nsZipItem* item = aArchive->GetItem(aEntryName.get());
+  nsZipItem* item = aArchive->GetItem(aEntryName);
   NS_ASSERTION(item, "failed to find zip entry");
 
   uint32_t bufSize = item->RealSize();
diff --git a/intl/hyphenation/glue/nsHyphenator.cpp b/intl/hyphenation/glue/nsHyphenator.cpp
index e506a3a423d..40ce45018b9 100644
--- a/intl/hyphenation/glue/nsHyphenator.cpp
+++ b/intl/hyphenation/glue/nsHyphenator.cpp
@@ -52,7 +52,7 @@ static const void* GetItemPtrFromJarURI(nsIJARURI* aJAR, uint32_t* aLength) {
   if (archive) {
     nsCString path;
     aJAR->GetJAREntry(path);
-    nsZipItem* item = archive->GetItem(path.get());
+    nsZipItem* item = archive->GetItem(path);
     if (item && item->Compression() == 0 && item->Size() > 0) {
       // We do NOT own this data, but it won't go away until the omnijar
       // file is closed during shutdown.
diff --git a/intl/locale/LocaleService.cpp b/intl/locale/LocaleService.cpp
index 1527f279103..7cb42fbb11c 100644
--- a/intl/locale/LocaleService.cpp
+++ b/intl/locale/LocaleService.cpp
@@ -338,7 +338,7 @@ static bool GetGREFileContents(const char* aFilePath, nsCString* aOutString) {
   // Look for the requested file in omnijar.
   RefPtr<nsZipArchive> zip = Omnijar::GetReader(Omnijar::GRE);
   if (zip) {
-    nsZipItemPtr<char> item(zip, aFilePath);
+    nsZipItemPtr<char> item(zip, nsDependentCString(aFilePath));
     if (!item) {
       return false;
     }
diff --git a/js/xpconnect/loader/URLPreloader.cpp b/js/xpconnect/loader/URLPreloader.cpp
index 1aa18aca44f..6721cd04711 100644
--- a/js/xpconnect/loader/URLPreloader.cpp
+++ b/js/xpconnect/loader/URLPreloader.cpp
@@ -402,7 +402,7 @@ void URLPreloader::BackgroundReadFiles() {
             entry->TypeString(), entry->mPath.get());
       }
 
-      auto item = zip->GetItem(entry->mPath.get());
+      auto item = zip->GetItem(entry->mPath);
       if (!item) {
         entry->mResultCode = NS_ERROR_FILE_NOT_FOUND;
         continue;
@@ -567,7 +567,7 @@ Result<nsCString, nsresult> URLPreloader::ReadURIInternal(nsIURI* uri,
   }
 
   // Not an Omnijar archive, so just read it directly.
-  FileLocation location(zip, PromiseFlatCString(path).BeginReading());
+  FileLocation location(zip, path);
   return URLEntry::ReadLocation(location);
 }
 
@@ -636,7 +636,7 @@ Result<FileLocation, nsresult> URLPreloader::CacheKey::ToFileLocation() {
   }
 
   RefPtr<nsZipArchive> zip = Archive();
-  return FileLocation(zip, mPath.get());
+  return FileLocation(zip, mPath);
 }
 
 Result<nsCString, nsresult> URLPreloader::URLEntry::Read() {
diff --git a/modules/libjar/nsJAR.cpp b/modules/libjar/nsJAR.cpp
index bc413190705..8193e72563f 100644
--- a/modules/libjar/nsJAR.cpp
+++ b/modules/libjar/nsJAR.cpp
@@ -135,8 +135,7 @@ nsJAR::OpenInner(nsIZipReader* aZipReader, const nsACString& aZipEntry) {
   {
     nsJAR* outerJAR = static_cast<nsJAR*>(aZipReader);
     RecursiveMutexAutoLock outerLock(outerJAR->mLock);
-    rv = nsZipHandle::Init(outerJAR->mZip.get(),
-                           PromiseFlatCString(aZipEntry).get(),
+    rv = nsZipHandle::Init(outerJAR->mZip.get(), aZipEntry,
                            getter_AddRefs(handle));
     NS_ENSURE_SUCCESS(rv, rv);
   }
@@ -191,8 +190,7 @@ nsJAR::Test(const nsACString& aEntryName) {
   if (!mZip) {
     return NS_ERROR_FAILURE;
   }
-  return mZip->Test(
-      aEntryName.IsEmpty() ? nullptr : PromiseFlatCString(aEntryName).get());
+  return mZip->Test(aEntryName);
 }
 
 NS_IMETHODIMP
@@ -205,7 +203,7 @@ nsJAR::Extract(const nsACString& aEntryName, nsIFile* outFile) {
   }
 
   LOG(("Extract[%p] %s", this, PromiseFlatCString(aEntryName).get()));
-  nsZipItem* item = mZip->GetItem(PromiseFlatCString(aEntryName).get());
+  nsZipItem* item = mZip->GetItem(aEntryName);
   NS_ENSURE_TRUE(item, NS_ERROR_FILE_NOT_FOUND);
 
   // Remove existing file or directory so we set permissions correctly.
@@ -245,7 +243,7 @@ nsJAR::GetEntry(const nsACString& aEntryName, nsIZipEntry** result) {
   if (!mZip) {
     return NS_ERROR_FAILURE;
   }
-  nsZipItem* zipItem = mZip->GetItem(PromiseFlatCString(aEntryName).get());
+  nsZipItem* zipItem = mZip->GetItem(aEntryName);
   NS_ENSURE_TRUE(zipItem, NS_ERROR_FILE_NOT_FOUND);
 
   RefPtr<nsJARItem> jarItem = new nsJARItem(zipItem);
@@ -261,7 +259,7 @@ nsJAR::HasEntry(const nsACString& aEntryName, bool* result) {
   if (!mZip) {
     return NS_ERROR_FAILURE;
   }
-  *result = mZip->GetItem(PromiseFlatCString(aEntryName).get()) != nullptr;
+  *result = mZip->GetItem(aEntryName) != nullptr;
   return NS_OK;
 }
 
@@ -301,7 +299,7 @@ nsJAR::GetInputStream(const nsACString& aEntryName, nsIInputStream** result) {
   const nsCString& entry = PromiseFlatCString(aEntryName);
   if (*entry.get()) {
     // First check if item exists in jar
-    item = mZip->GetItem(entry.get());
+    item = mZip->GetItem(entry);
     if (!item) return NS_ERROR_FILE_NOT_FOUND;
   }
   RefPtr<nsJARInputStream> jis = new nsJARInputStream();
diff --git a/modules/libjar/nsJARInputStream.cpp b/modules/libjar/nsJARInputStream.cpp
index 83f8f3c224e..8095f9edf12 100644
--- a/modules/libjar/nsJARInputStream.cpp
+++ b/modules/libjar/nsJARInputStream.cpp
@@ -341,7 +341,8 @@ nsresult nsJARInputStream::ReadDirectory(char* aBuffer, uint32_t aCount,
 
       const char* entryName = mArray[mArrPos].get();
       uint32_t entryNameLen = mArray[mArrPos].Length();
-      nsZipItem* ze = mJar->mZip->GetItem(entryName);
+      nsZipItem* ze = mJar->mZip->GetItem(
+          nsDependentCString(mArray[mArrPos].get(), mArray[mArrPos].Length()));
       NS_ENSURE_TRUE(ze, NS_ERROR_FILE_NOT_FOUND);
 
       // Last Modified Time
diff --git a/modules/libjar/nsZipArchive.cpp b/modules/libjar/nsZipArchive.cpp
index cf894dc9d1e..dcbd9327b92 100644
--- a/modules/libjar/nsZipArchive.cpp
+++ b/modules/libjar/nsZipArchive.cpp
@@ -237,12 +237,12 @@ nsresult nsZipHandle::Init(nsIFile* file, nsZipHandle** ret, PRFileDesc** aFd) {
   return NS_OK;
 }
 
-nsresult nsZipHandle::Init(nsZipArchive* zip, const char* entry,
+nsresult nsZipHandle::Init(nsZipArchive* zip, const nsACString& entry,
                            nsZipHandle** ret) {
   RefPtr<nsZipHandle> handle = new nsZipHandle();
   if (!handle) return NS_ERROR_OUT_OF_MEMORY;
 
-  LOG(("ZipHandle::Init entry %s", entry));
+  LOG(("ZipHandle::Init entry %s", PromiseFlatCString(entry).get()));
 
   nsZipItem* item = zip->GetItem(entry);
   if (item && item->Compression() == DEFLATED &&
@@ -414,10 +414,10 @@ already_AddRefed<nsZipArchive> nsZipArchive::OpenArchive(nsIFile* aFile) {
 //---------------------------------------------
 //  nsZipArchive::Test
 //---------------------------------------------
-nsresult nsZipArchive::Test(const char* aEntryName) {
+nsresult nsZipArchive::Test(const nsACString& aEntryName) {