diff --git a/netwerk/protocol/http/HttpBaseChannel.cpp b/netwerk/protocol/http/HttpBaseChannel.cpp
index b47cc0287c53..7535d27f19e8 100644
--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -1580,7 +1580,7 @@ HttpBaseChannel::SetupReplacementChannel(nsIURI       *newURI,
           if (clen) {
             uploadChannel->SetUploadStream(mUploadStream,
                                            nsDependentCString(ctype),
-                                           atoi(clen));
+                                           nsCRT::atoll(clen));
           }
         }
       }
diff --git a/netwerk/streamconv/converters/nsMultiMixedConv.cpp b/netwerk/streamconv/converters/nsMultiMixedConv.cpp
index e64a9e885a14..1c8aea5aa5a6 100644
--- a/netwerk/streamconv/converters/nsMultiMixedConv.cpp
+++ b/netwerk/streamconv/converters/nsMultiMixedConv.cpp
@@ -954,7 +954,7 @@ nsMultiMixedConv::ParseHeaders(nsIChannel *aChannel, char *&aPtr,
             if (headerStr.LowerCaseEqualsLiteral("content-type")) {
                 mContentType = headerVal;
             } else if (headerStr.LowerCaseEqualsLiteral("content-length")) {
-                mContentLength = atoi(headerVal.get()); // XXX 64-bit math?
+                mContentLength = nsCRT::atoll(headerVal.get());
             } else if (headerStr.LowerCaseEqualsLiteral("content-disposition")) {
                 mContentDisposition = headerVal;
             } else if (headerStr.LowerCaseEqualsLiteral("set-cookie")) {
@@ -988,14 +988,14 @@ nsMultiMixedConv::ParseHeaders(nsIChannel *aChannel, char *&aPtr,
                     
                     tmpPtr[0] = '\0';
                     
-                    mByteRangeStart = atoi(range); // XXX want 64-bit conv
+                    mByteRangeStart = nsCRT::atoll(range);
                     tmpPtr++;
-                    mByteRangeEnd = atoi(tmpPtr);
+                    mByteRangeEnd = nsCRT::atoll(tmpPtr);
                 }
 
                 mIsByteRangeRequest = true;
                 if (mContentLength == LL_MAXUINT)
-                    mContentLength = uint64_t(int64_t(mByteRangeEnd - mByteRangeStart + int64_t(1)));
+                    mContentLength = uint64_t(mByteRangeEnd - mByteRangeStart + 1);
             }
         }
         *newLine = tmpChar;