diff --git a/indra/llimage/llpngwrapper.cpp b/indra/llimage/llpngwrapper.cpp
index 4292f29acc128c3023199be9f57c892655152a1b..531859cbc9ebdb4fc522f2b4e23b2f45c8489862 100644
--- a/indra/llimage/llpngwrapper.cpp
+++ b/indra/llimage/llpngwrapper.cpp
@@ -33,10 +33,12 @@
 
 #include <stdexcept>
 
+namespace {
 struct PngError: public std::runtime_error
 {
     PngError(png_const_charp msg): std::runtime_error(msg) {}
 };
+} // anonymous namespace
 
 // ---------------------------------------------------------------------------
 // LLPngWrapper