diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5c29ba833..1b4627a20 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -147,7 +147,7 @@ function (extract_make_variable variable makefile_source)
   set (${variable} ${listVar} PARENT_SCOPE)
 endfunction ()
 
-# http://stackoverflow.com/a/27630120
+# https://stackoverflow.com/a/27630120
 function (add_prefix_to_list var prefix)
   set (listVar "")
   foreach (f ${${var}})
diff --git a/m4/ax_cxx_compile_stdcxx.m4 b/m4/ax_cxx_compile_stdcxx.m4
index 5032bba80..8b6df5a5d 100644
--- a/m4/ax_cxx_compile_stdcxx.m4
+++ b/m4/ax_cxx_compile_stdcxx.m4
@@ -422,7 +422,7 @@ namespace cxx11
 
   }
 
-  // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
+  // https://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
   // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
   // because of this.
   namespace test_template_alias_sfinae