diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index aedadfa7c..00f96274e 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -169,16 +169,6 @@ if(CMARK_SHARED OR CMARK_STATIC)
 
 endif()
 
-# Feature tests
-include(CheckCSourceCompiles)
-CHECK_C_SOURCE_COMPILES(
-  "int main() { __builtin_expect(0,0); return 0; }"
-  HAVE___BUILTIN_EXPECT)
-
-CONFIGURE_FILE(
-  ${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
-  ${CMAKE_CURRENT_BINARY_DIR}/config.h)
-
 if(CMARK_LIB_FUZZER)
   add_executable(cmark-fuzz ../test/cmark-fuzz.c ${LIBRARY_SOURCES})
   cmark_add_compile_options(cmark-fuzz)
diff --git a/src/blocks.c b/src/blocks.c
index 59bb22252..1abff0514 100644
--- a/src/blocks.c
+++ b/src/blocks.c
@@ -12,7 +12,6 @@
 #include <stdlib.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "parser.h"
 #include "cmark.h"
 #include "node.h"
diff --git a/src/buffer.c b/src/buffer.c
index 4ad03d7c9..aeca03d09 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -7,7 +7,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark_ctype.h"
 #include "buffer.h"
 
diff --git a/src/buffer.h b/src/buffer.h
index 7dfb1f8b3..430500bac 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -1,12 +1,12 @@
 #ifndef CMARK_BUFFER_H
 #define CMARK_BUFFER_H
 
-#include <stddef.h>
-#include <stdarg.h>
-#include <string.h>
 #include <limits.h>
+#include <stdarg.h>
+#include <stddef.h>
 #include <stdint.h>
-#include "config.h"
+#include <string.h>
+
 #include "cmark.h"
 
 #ifdef __cplusplus
diff --git a/src/commonmark.c b/src/commonmark.c
index dc31f4597..3c4347668 100644
--- a/src/commonmark.c
+++ b/src/commonmark.c
@@ -5,7 +5,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"
diff --git a/src/config.h.in b/src/config.h.in
deleted file mode 100644
index f67fb6326..000000000
--- a/src/config.h.in
+++ /dev/null
@@ -1,14 +0,0 @@
-#ifndef CMARK_CONFIG_H
-#define CMARK_CONFIG_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#cmakedefine HAVE___BUILTIN_EXPECT
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif
diff --git a/src/houdini.h b/src/houdini.h
index f738e8243..410530631 100644
--- a/src/houdini.h
+++ b/src/houdini.h
@@ -6,16 +6,8 @@ extern "C" {
 #endif
 
 #include <stdint.h>
-#include "config.h"
-#include "buffer.h"
 
-#ifdef HAVE___BUILTIN_EXPECT
-#define likely(x) __builtin_expect((x), 1)
-#define unlikely(x) __builtin_expect((x), 0)
-#else
-#define likely(x) (x)
-#define unlikely(x) (x)
-#endif
+#include "buffer.h"
 
 #ifdef HOUDINI_USE_LOCALE
 #define _isxdigit(c) isxdigit(c)
diff --git a/src/houdini_href_e.c b/src/houdini_href_e.c
index 959d4bb63..38f2a5826 100644
--- a/src/houdini_href_e.c
+++ b/src/houdini_href_e.c
@@ -4,6 +4,17 @@
 
 #include "houdini.h"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /*
  * The following characters will not be escaped:
  *
diff --git a/src/houdini_html_e.c b/src/houdini_html_e.c
index 0e539f037..391f2eaa1 100644
--- a/src/houdini_html_e.c
+++ b/src/houdini_html_e.c
@@ -4,6 +4,17 @@
 
 #include "houdini.h"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /**
  * According to the OWASP rules:
  *
diff --git a/src/houdini_html_u.c b/src/houdini_html_u.c
index 3b7466e5f..e0999b0ae 100644
--- a/src/houdini_html_u.c
+++ b/src/houdini_html_u.c
@@ -7,6 +7,17 @@
 #include "utf8.h"
 #include "entities.inc"
 
+#if !defined(__has_builtin)
+# define __has_builtin(b) 0
+#endif
+
+#if !__has_builtin(__builtin_expect)
+# define __builtin_expect(e, v) (e)
+#endif
+
+#define likely(e) __builtin_expect((e), 1)
+#define unlikely(e) __builtin_expect((e), 0)
+
 /* Binary tree lookup code for entities added by JGM */
 
 static const unsigned char *S_lookup(int i, int low, int hi,
diff --git a/src/html.c b/src/html.c
index e9e29141a..35ce52226 100644
--- a/src/html.c
+++ b/src/html.c
@@ -5,7 +5,6 @@
 #include <string.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"
diff --git a/src/inlines.c b/src/inlines.c
index 8314c846a..c0b1c55d2 100644
--- a/src/inlines.c
+++ b/src/inlines.c
@@ -4,7 +4,6 @@
 #include <string.h>
 
 #include "cmark_ctype.h"
-#include "config.h"
 #include "node.h"
 #include "parser.h"
 #include "references.h"
diff --git a/src/iterator.c b/src/iterator.c
index d41b90d69..cc428285e 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -2,7 +2,6 @@
 #include <stdbool.h>
 #include <stdlib.h>
 
-#include "config.h"
 #include "node.h"
 #include "cmark.h"
 #include "iterator.h"
diff --git a/src/latex.c b/src/latex.c
index 1b7b6c572..61be34f95 100644
--- a/src/latex.c
+++ b/src/latex.c
@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"
diff --git a/src/main.c b/src/main.c
index e02a3c438..e63604bd7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,8 +1,8 @@
-#include <stdlib.h>
+#include <errno.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <errno.h>
-#include "config.h"
+
 #include "cmark.h"
 #include "node.h"
 
diff --git a/src/man.c b/src/man.c
index c793a05fa..02dfb7cb3 100644
--- a/src/man.c
+++ b/src/man.c
@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"
diff --git a/src/node.c b/src/node.c
index bcf96316d..48f6fd758 100644
--- a/src/node.c
+++ b/src/node.c
@@ -2,7 +2,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "node.h"
 
 static void S_node_unlink(cmark_node *node);
diff --git a/src/node.h b/src/node.h
index 430ee5671..c6591b03b 100644
--- a/src/node.h
+++ b/src/node.h
@@ -9,7 +9,6 @@ extern "C" {
 #include <stdint.h>
 #include <stdio.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "buffer.h"
 
diff --git a/src/xml.c b/src/xml.c
index a69053e5c..4f16edcde 100644
--- a/src/xml.c
+++ b/src/xml.c
@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "config.h"
 #include "cmark.h"
 #include "node.h"
 #include "buffer.h"