--- /dev/null
+++ a/opus_buildtype.cmake
@@ -0,0 +1,23 @@
+# Set a default build type if none was specified
+
+if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
+  if(CMAKE_C_FLAGS)
+    message(STATUS "CMAKE_C_FLAGS: " ${CMAKE_C_FLAGS})
+  else()
+    set(default_build_type "Release")
+    message(
+      STATUS
+        "Setting build type to '${default_build_type}' as none was specified and no CFLAGS was exported."
+      )
+    set(CMAKE_BUILD_TYPE "${default_build_type}"
+        CACHE STRING "Choose the type of build."
+        FORCE)
+    # Set the possible values of build type for cmake-gui
+    set_property(CACHE CMAKE_BUILD_TYPE
+                 PROPERTY STRINGS
+                          "Debug"
+                          "Release"
+                          "MinSizeRel"
+                          "RelWithDebInfo")
+  endif()
+endif()