diff --git a/compiler/optimizing/optimization.cc b/compiler/optimizing/optimization.cc
index 2b7bedd..e0c5933 100644
--- a/compiler/optimizing/optimization.cc
+++ b/compiler/optimizing/optimization.cc
@@ -58,7 +58,7 @@
 
 // Decide between default or alternative pass name.
 
-namespace art {
+namespace art HIDDEN {
 
 const char* OptimizationPassName(OptimizationPass pass) {
   switch (pass) {