diff --git a/Modules/Platform/HP-UX.cmake b/Modules/Platform/HP-UX.cmake
index c1449a877..b4e750678 100644
--- a/Modules/Platform/HP-UX.cmake
+++ b/Modules/Platform/HP-UX.cmake
@@ -41,8 +41,8 @@ ELSE(CMAKE_COMPILER_IS_GNUCXX)
   SET(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG "-Wl,+b")       # -rpath
   SET (CMAKE_CXX_FLAGS_INIT "")
   SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-  SET (CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-O3")
-  SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O2")
+  SET (CMAKE_CXX_FLAGS_MINSIZEREL_INIT "+O3")
+  SET (CMAKE_CXX_FLAGS_RELEASE_INIT "+O2")
   SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g")
   SET (CMAKE_C_FLAGS_INIT "")