diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 36cd85c0541..7aaf8590740 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -523,6 +523,9 @@ IF(MSVC)
   SET_SOURCE_FILES_PROPERTIES(${QGIS_CORE_MOC_SRCS} PROPERTIES COMPILE_FLAGS "/wd4512 /wd4996" )
 ELSE(MSVC)
   SET_SOURCE_FILES_PROPERTIES(${QGIS_CORE_MOC_SRCS} PROPERTIES COMPILE_FLAGS "-Wno-deprecated-declarations" )
+  IF ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" AND (CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES RelWithDebInfo))
+    SET_SOURCE_FILES_PROPERTIES(${CMAKE_CURRENT_SOURCE_DIR}/qgsexpression_texts.cpp PROPERTIES COMPILE_FLAGS "-O1")
+  ENDIF ()
 ENDIF(MSVC)
 
 # install headers