diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index f35aa36b..97ef730b 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -1678,6 +1678,10 @@ XML_ParseBuffer(XML_Parser parser, int len, int isFinal)
 void * XMLCALL
 XML_GetBuffer(XML_Parser parser, int len)
 {
+  if (len < 0) {
+    errorCode = XML_ERROR_NO_MEMORY;
+    return NULL;
+  }
   switch (ps_parsing) {
   case XML_SUSPENDED:
     errorCode = XML_ERROR_SUSPENDED;
@@ -1689,8 +1693,11 @@ XML_GetBuffer(XML_Parser parser, int len)
   }
 
   if (len > bufferLim - bufferEnd) {
-    /* FIXME avoid integer overflow */
     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);
 
@@ -1719,7 +1726,11 @@ XML_GetBuffer(XML_Parser parser, int len)
         bufferSize = INIT_BUFFER_SIZE;
       do {
         bufferSize *= 2;
-      } while (bufferSize < neededSize);
+      } while (bufferSize < neededSize && bufferSize > 0);
+      if (bufferSize <= 0) {
+        errorCode = XML_ERROR_NO_MEMORY;
+        return NULL;
+      }
       newBuf = (char *)MALLOC(bufferSize);
       if (newBuf == 0) {
         errorCode = XML_ERROR_NO_MEMORY;