diff --git a/mkspecs/linux-g++-32/qmake.conf b/mkspecs/linux-g++-32/qmake.conf
index 340aa85..571a559 100644
--- a/mkspecs/linux-g++-32/qmake.conf
+++ b/mkspecs/linux-g++-32/qmake.conf
@@ -9,6 +9,8 @@ QMAKE_INCREMENTAL_STYLE = sublib
 QMAKE_CFLAGS            = -m32
 QMAKE_LFLAGS            = -m32
 
+QMAKE_CFLAGS_RELEASE   += -O2
+
 include(../common/linux.conf)
 include(../common/gcc-base-unix.conf)
 include(../common/g++-unix.conf)
diff --git a/mkspecs/linux-g++-64/qmake.conf b/mkspecs/linux-g++-64/qmake.conf
index 36fb6a8..9a07595 100644
--- a/mkspecs/linux-g++-64/qmake.conf
+++ b/mkspecs/linux-g++-64/qmake.conf
@@ -12,6 +12,8 @@ QMAKE_INCREMENTAL_STYLE = sublib
 QMAKE_CFLAGS            = -m64
 QMAKE_LFLAGS            = -m64
 
+QMAKE_CFLAGS_RELEASE   += -O2
+
 include(../common/linux.conf)
 include(../common/gcc-base-unix.conf)
 include(../common/g++-unix.conf)
diff --git a/mkspecs/linux-g++/qmake.conf b/mkspecs/linux-g++/qmake.conf
index 35bce8f..5186f98 100644
--- a/mkspecs/linux-g++/qmake.conf
+++ b/mkspecs/linux-g++/qmake.conf
@@ -6,6 +6,8 @@ MAKEFILE_GENERATOR      = UNIX
 CONFIG                 += incremental
 QMAKE_INCREMENTAL_STYLE = sublib
 
+QMAKE_CFLAGS_RELEASE   += -O2
+
 include(../common/linux.conf)
 include(../common/gcc-base-unix.conf)
 include(../common/g++-unix.conf)