diff --git a/src/expat/lib/xmlparse.c b/src/expat/lib/xmlparse.c
index e3d77a5a26..4dd2cf989a 100644
--- a/src/expat/lib/xmlparse.c
+++ b/src/expat/lib/xmlparse.c
@@ -1703,14 +1703,15 @@ XML_GetBuffer(XML_Parser parser, int len)
   }
 
   if (len > bufferLim - bufferEnd) {
+#ifdef XML_CONTEXT_BYTES
+    int keep = (int)(bufferPtr - buffer);
+#endif /* defined XML_CONTEXT_BYTES */
     int neededSize = len + (int)(bufferEnd - bufferPtr);
     if (neededSize < 0) {
       errorCode = XML_ERROR_NO_MEMORY;
       return NULL;
     }
 #ifdef XML_CONTEXT_BYTES
-    int keep = (int)(bufferPtr - buffer);
-
     if (keep > XML_CONTEXT_BYTES)
       keep = XML_CONTEXT_BYTES;
     neededSize += keep;