diff --git a/intl/strres/src/nsStringBundle.cpp b/intl/strres/src/nsStringBundle.cpp
index 6ebb5c9ca504..13da09708036 100644
--- a/intl/strres/src/nsStringBundle.cpp
+++ b/intl/strres/src/nsStringBundle.cpp
@@ -385,7 +385,7 @@ nsStringBundle::FormatString(const PRUnichar *aFormatStr,
   // Don't believe me? See:
   //   http://www.eskimo.com/~scs/C-faq/q15.13.html
   // -alecf
-  *aResult = 
+  PRUnichar *text = 
     nsTextFormatter::smprintf(aFormatStr,
                               aLength >= 1 ? aParams[0] : nsnull,
                               aLength >= 2 ? aParams[1] : nsnull,
@@ -397,7 +397,21 @@ nsStringBundle::FormatString(const PRUnichar *aFormatStr,
                               aLength >= 8 ? aParams[7] : nsnull,
                               aLength >= 9 ? aParams[8] : nsnull,
                               aLength >= 10 ? aParams[9] : nsnull);
-  return NS_OK;
+
+  if (!text) {
+    *aResult = nsnull;
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  // nsTextFormatter does not use the shared nsMemory allocator.
+  // Instead it is required to free the memory it allocates using
+  // nsTextFormatter::smprintf_free.  Let's instead use nsMemory based
+  // allocation for the result that we give out and free the string
+  // returned by smprintf ourselves!
+  *aResult = NS_strdup(text);
+  nsTextFormatter::smprintf_free(text);
+
+  return *aResult ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
 }
 
 NS_IMPL_ISUPPORTS1(nsExtensibleStringBundle, nsIStringBundle)