diff --git a/intl/uconv/nsConverterInputStream.cpp b/intl/uconv/nsConverterInputStream.cpp
index 365342af6d6..f871b50801e 100644
--- a/intl/uconv/nsConverterInputStream.cpp
+++ b/intl/uconv/nsConverterInputStream.cpp
@@ -19,6 +19,14 @@ NS_IMPL_ISUPPORTS(nsConverterInputStream, nsIConverterInputStream,
 NS_IMETHODIMP
 nsConverterInputStream::Init(nsIInputStream* aStream, const char* aCharset,
                              int32_t aBufferSize, char16_t aReplacementChar) {
+  mInput = nullptr;
+  mByteData.Clear();
+  mUnicharData.Clear();
+  mLastErrorCode = NS_OK;
+  mLeftOverBytes = 0;
+  mUnicharDataOffset = 0;
+  mUnicharDataLength = 0;
+
   nsAutoCString label;
   if (!aCharset) {
     label.AssignLiteral("UTF-8");