diff --git a/CMakeLists.txt b/CMakeLists.txt
index b5f7f55b..a54a9493 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -131,8 +131,13 @@ check_symbol_exists(funopen stdio.h HAVE_OPEN_FUNOPEN)
 check_symbol_exists(fopencookie stdio.h HAVE_OPEN_FOPENCOOKIE)
 
 if(NOT HAVE_OPEN_MEMSTREAM)
-  if (HAVE_OPEN_FUNOPEN AND HAVE_OPEN_FOPENCOOKIE)
-    message(STATUS "using open_memstream implementation")
+  if (HAVE_OPEN_FUNOPEN)
+    message(STATUS "implementing open_memstream using funopen()")
+    target_compile_definitions(tinycbor PRIVATE HAVE_OPEN_FUNOPEN)
+    target_sources(tinycbor PRIVATE src/open_memstream.c)
+  elseif (HAVE_OPEN_FOPENCOOKIE)
+    message(STATUS "implementing open_memstream using fopencookie()")
+    target_compile_definitions(tinycbor PRIVATE HAVE_OPEN_FOPENCOOKIE)
     target_sources(tinycbor PRIVATE src/open_memstream.c)
   else()
     target_compile_definitions(tinycbor PRIVATE WITHOUT_OPEN_MEMSTREAM)
diff --git a/src/open_memstream.c b/src/open_memstream.c
index 33653784..ed94e898 100644
--- a/src/open_memstream.c
+++ b/src/open_memstream.c
@@ -35,10 +35,10 @@
 #if defined(__unix__) || defined(__APPLE__)
 #  include <unistd.h>
 #endif
-#ifdef __APPLE__
+#if defined(HAVE_OPEN_FUNOPEN)
 typedef int RetType;
 typedef int LenType;
-#elif __linux__
+#elif defined(HAVE_OPEN_FOPENCOOKIE)
 typedef ssize_t RetType;
 typedef size_t LenType;
 #else
@@ -99,9 +99,9 @@ FILE *open_memstream(char **bufptr, size_t *lenptr)
     *bufptr = NULL;
     *lenptr = 0;
 
-#ifdef __APPLE__
+#if defined(HAVE_OPEN_FUNOPEN)
     return funopen(b, NULL, write_to_buffer, NULL, close_buffer);
-#elif __linux__
+#elif defined(HAVE_OPEN_FOPENCOOKIE)
     static const cookie_io_functions_t vtable = {
         NULL,
         write_to_buffer,