diff --git a/configure b/configure
index a96786c9d36f938dbaed0db9206167cf1f1d0d83..a5b760fed71a180c7a92e160275d6e84bdaa2e0a 100755
--- a/configure
+++ b/configure
@@ -2259,6 +2259,8 @@ $as_echo "$as_me: creating cache $cache_file" >&6;}
 fi
 
 as_fn_append ac_header_list " sqlite3.h"
+as_fn_append ac_header_list " curl/curl.h"
+as_fn_append ac_header_list " json-c/json.h"
 as_fn_append ac_header_list " stdnoreturn.h"
 as_fn_append ac_header_list " stddef.h"
 as_fn_append ac_header_list " inttypes.h"
@@ -3820,6 +3822,10 @@ done
 
 
 
+
+
+
+
 
 
 
@@ -13569,7 +13575,7 @@ if test "x${LKT_DEBUG_ENABLED}" = "xyes"; then
 else
     BASEFLAGS+=" -O3"
 fi
-CFLAGS="${BASEFLAGS} -std=c18"
+CFLAGS="${BASEFLAGS} -std=c11"
 
 ##########
 # OUTPUT #
diff --git a/configure.ac b/configure.ac
index c1f7102e1453682dd2f75fc451c228be857f06a0..4a5f7dfe39671a375f257cea161342f131ae6347 100644
--- a/configure.ac
+++ b/configure.ac
@@ -22,6 +22,8 @@ AS_IF([test "$LKT_PATH_SOURCE" = "$LKT_PATH_BUILD"],
 AC_CHECK_LIB([sqlite3], [sqlite3_open_v2])
 AC_CHECK_HEADERS_ONCE([
     sqlite3.h
+    curl/curl.h
+    json-c/json.h
     stdnoreturn.h
     stddef.h
     inttypes.h
diff --git a/inc/lektor/lktconfig.h.in b/inc/lektor/lktconfig.h.in
index 58c06167260a6d9736245a0f4f062bb7a0148d93..833b96d19dd348b08db54231b44b31647d5db6d9 100644
--- a/inc/lektor/lktconfig.h.in
+++ b/inc/lektor/lktconfig.h.in
@@ -6,6 +6,9 @@
 /* Define to 1 if you have the <ctypes.h> header file. */
 #undef HAVE_CTYPES_H
 
+/* Define to 1 if you have the <curl/curl.h> header file. */
+#undef HAVE_CURL_CURL_H
+
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #undef HAVE_DLFCN_H
 
@@ -15,6 +18,9 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
+/* Define to 1 if you have the <json-c/json.h> header file. */
+#undef HAVE_JSON_C_JSON_H
+
 /* Define to 1 if you have the `sqlite3' library (-lsqlite3). */
 #undef HAVE_LIBSQLITE3