diff --git a/mozilla/editor/libeditor/txtsvc/nsTextServicesDocument.cpp b/mozilla/editor/libeditor/txtsvc/nsTextServicesDocument.cpp
index 87ce8e8243d..37c9fcdf638 100644
--- a/mozilla/editor/libeditor/txtsvc/nsTextServicesDocument.cpp
+++ b/mozilla/editor/libeditor/txtsvc/nsTextServicesDocument.cpp
@@ -390,7 +390,7 @@ nsTextServicesDocument::GetCurrentTextBlock(nsString *aStr)
   if (!aStr)
     return NS_ERROR_NULL_POINTER;
 
-  *aStr = "";
+  aStr->SetLength(0);
 
   if (!mIterator)
     return NS_ERROR_FAILURE;
@@ -4152,7 +4152,7 @@ nsTextServicesDocument::CreateOffsetTable(nsString *aStr)
   ClearOffsetTable();
 
   if (aStr)
-    *aStr = "";
+    aStr->SetLength(0);
 
   if (mIteratorStatus == nsTextServicesDocument::eIsDone)
     return NS_OK;
diff --git a/mozilla/editor/txtsvc/src/nsTextServicesDocument.cpp b/mozilla/editor/txtsvc/src/nsTextServicesDocument.cpp
index 87ce8e8243d..37c9fcdf638 100644
--- a/mozilla/editor/txtsvc/src/nsTextServicesDocument.cpp
+++ b/mozilla/editor/txtsvc/src/nsTextServicesDocument.cpp
@@ -390,7 +390,7 @@ nsTextServicesDocument::GetCurrentTextBlock(nsString *aStr)
   if (!aStr)
     return NS_ERROR_NULL_POINTER;
 
-  *aStr = "";
+  aStr->SetLength(0);
 
   if (!mIterator)
     return NS_ERROR_FAILURE;
@@ -4152,7 +4152,7 @@ nsTextServicesDocument::CreateOffsetTable(nsString *aStr)
   ClearOffsetTable();
 
   if (aStr)
-    *aStr = "";
+    aStr->SetLength(0);
 
   if (mIteratorStatus == nsTextServicesDocument::eIsDone)
     return NS_OK;