diff --git a/CMakeLists.txt b/CMakeLists.txt
index fc654747fca..67cc80c18ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -153,14 +153,24 @@ if(WIN32)
 endif()
 
  # Use C99 standard
-set(CMAKE_C_STANDARD 99)
+if (NOT DEFINED CMAKE_C_STANDARD)
+  set(CMAKE_C_STANDARD 99)
+endif()
 
 # Add c++11 flags
-set(CMAKE_CXX_STANDARD 11)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSIONS OFF)
+if (NOT DEFINED CMAKE_CXX_STANDARD)
+  set(CMAKE_CXX_STANDARD 11)
+endif()
+if (NOT DEFINED CMAKE_CXX_STANDARD_REQUIRED)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+endif()
+if (NOT DEFINED CMAKE_CXX_EXTENSIONS)
+  set(CMAKE_CXX_EXTENSIONS OFF)
+endif()
 
-set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+if (NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
+  set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+endif()
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 if(MSVC)
diff --git a/templates/CMakeLists.txt.template b/templates/CMakeLists.txt.template
index 24fa7f0eb96..9f77410a7e4 100644
--- a/templates/CMakeLists.txt.template
+++ b/templates/CMakeLists.txt.template
@@ -243,15 +243,25 @@
   endif()
 
    # Use C99 standard
-  set(CMAKE_C_STANDARD 99)
+  if (NOT DEFINED CMAKE_C_STANDARD)
+    set(CMAKE_C_STANDARD 99)
+  endif()
 
   # Add c++11 flags
-  set(CMAKE_CXX_STANDARD 11)
-  set(CMAKE_CXX_STANDARD_REQUIRED ON)
-  set(CMAKE_CXX_EXTENSIONS OFF)
+  if (NOT DEFINED CMAKE_CXX_STANDARD)
+    set(CMAKE_CXX_STANDARD 11)
+  endif()
+  if (NOT DEFINED CMAKE_CXX_STANDARD_REQUIRED)
+    set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  endif()
+  if (NOT DEFINED CMAKE_CXX_EXTENSIONS)
+    set(CMAKE_CXX_EXTENSIONS OFF)
+  endif()
 
   ## Some libraries are shared even with BUILD_SHARED_LIBRARIES=OFF
-  set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+  if (NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
+    set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+  endif()
   list(APPEND CMAKE_MODULE_PATH "<%text>${CMAKE_CURRENT_SOURCE_DIR}</%text>/cmake/modules")
 
   if(MSVC)