diff --git a/htmlparser/src/nsWellFormedDTD.cpp b/htmlparser/src/nsWellFormedDTD.cpp
index 2ecfd90460e..dfd13653e1c 100644
--- a/htmlparser/src/nsWellFormedDTD.cpp
+++ b/htmlparser/src/nsWellFormedDTD.cpp
@@ -453,7 +453,7 @@ void GetProcessingInstruction(const nsString& aPIString, char* a_PI)
     nsString temp;
     PRInt32 theOffset = aPIString.FindCharInSet(theWS2,1);
     aPIString.Mid(temp,1,theOffset);
-    temp.ToCString(a_PI,temp.Length());
+    temp.ToCString(a_PI,30);
   }
   return;
 }
diff --git a/parser/htmlparser/src/nsWellFormedDTD.cpp b/parser/htmlparser/src/nsWellFormedDTD.cpp
index 2ecfd90460e..dfd13653e1c 100644
--- a/parser/htmlparser/src/nsWellFormedDTD.cpp
+++ b/parser/htmlparser/src/nsWellFormedDTD.cpp
@@ -453,7 +453,7 @@ void GetProcessingInstruction(const nsString& aPIString, char* a_PI)
     nsString temp;
     PRInt32 theOffset = aPIString.FindCharInSet(theWS2,1);
     aPIString.Mid(temp,1,theOffset);
-    temp.ToCString(a_PI,temp.Length());
+    temp.ToCString(a_PI,30);
   }
   return;
 }