diff --git a/indra/llmessage/aicurl.cpp b/indra/llmessage/aicurl.cpp
index 4cc9eadb3..cbb5fcc45 100644
--- a/indra/llmessage/aicurl.cpp
+++ b/indra/llmessage/aicurl.cpp
@@ -308,9 +308,10 @@ LLAtomicU32 Stats::llsd_body_count;
 LLAtomicU32 Stats::llsd_body_parse_error;
 LLAtomicU32 Stats::raw_body_count;
 
+// Called from BufferedCurlEasyRequest::setStatusAndReason.
+// The only allowed values for 'status' are S <= status < S+20, where S={100,200,300,400,500}.
 U32 Stats::status2index(U32 status)
 {
-  llassert_always(status >= 100 && status < 600 && (status % 100) < 20);	// Max value 519.
   return (status - 100) / 100 * 20 + status % 100;							// Returns 0..99 (for status 100..519).
 }
 
diff --git a/indra/llmessage/aicurlthread.cpp b/indra/llmessage/aicurlthread.cpp
index 194e23ddf..3dc3bd3e2 100644
--- a/indra/llmessage/aicurlthread.cpp
+++ b/indra/llmessage/aicurlthread.cpp
@@ -2268,7 +2268,11 @@ void BufferedCurlEasyRequest::setStatusAndReason(U32 status, std::string const&
 {
   mStatus = status;
   mReason = reason;
-  AICurlInterface::Stats::status_count[AICurlInterface::Stats::status2index(mStatus)]++;
+  if (status >= 100 && status < 600 && (status % 100) < 20)
+  {
+	// Only count statistic for sane values.
+	AICurlInterface::Stats::status_count[AICurlInterface::Stats::status2index(mStatus)]++;
+  }
 
   // Sanity check. If the server replies with a redirect status then we better have that option turned on!
   if ((status >= 300 && status < 400) && mResponder && !mResponder->redirect_status_ok())
@@ -2419,23 +2423,31 @@ size_t BufferedCurlEasyRequest::curlHeaderCallback(char* data, size_t size, size
 	std::string::iterator pos2 = std::find(pos1, end, ' ');
 	if (pos2 != end) ++pos2;
 	std::string::iterator pos3 = std::find(pos2, end, '\r');
-	U32 status;
+	U32 status = 0;
 	std::string reason;
 	if (pos3 != end && std::isdigit(*pos1))
 	{
 	  status = atoi(&header_line[pos1 - begin]);
 	  reason.assign(pos2, pos3);
 	}
-	else
+	if (!(status >= 100 && status < 600 && (status % 100) < 20))	// Sanity check on the decoded status.
 	{
+	  if (status == 0)
+	  {
+		reason = "Header parse error.";
+		llwarns << "Received broken header line from server: \"" << header << "\"" << llendl;
+	  }
+	  else
+	  {
+		reason = "Unexpected HTTP status.";
+		llwarns << "Received unexpected status value from server (" << status << "): \"" << header << "\"" << llendl;
+	  }
+	  // Either way, this status value is not understood (or taken into account).
+	  // Set it to internal error so that the rest of code treats it as an error.
 	  status = HTTP_INTERNAL_ERROR;
-	  reason = "Header parse error.";
-	  llwarns << "Received broken header line from server: \"" << header << "\"" << llendl;
-	}
-	{
-	  self_w->received_HTTP_header();
-	  self_w->setStatusAndReason(status, reason);
 	}
+	self_w->received_HTTP_header();
+	self_w->setStatusAndReason(status, reason);
 	return header_len;
   }