Don't check for open.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 40e17c2..8f95639 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -151,7 +151,6 @@
CHECK_FUNCTION_EXISTS(ftello HAVE_FTELLO)
CHECK_FUNCTION_EXISTS(getprogname HAVE_GETPROGNAME)
CHECK_FUNCTION_EXISTS(localtime_r HAVE_LOCALTIME_R)
-CHECK_FUNCTION_EXISTS(open HAVE_OPEN)
CHECK_FUNCTION_EXISTS(setmode HAVE_SETMODE)
CHECK_FUNCTION_EXISTS(snprintf HAVE_SNPRINTF)
CHECK_FUNCTION_EXISTS(strcasecmp HAVE_STRCASECMP)
diff --git a/cmake-config.h.in b/cmake-config.h.in
index 07e174f..de6a97e 100644
--- a/cmake-config.h.in
+++ b/cmake-config.h.in
@@ -34,7 +34,6 @@
#cmakedefine HAVE_MBEDTLS
#cmakedefine HAVE_MKSTEMP
#cmakedefine HAVE_NULLABLE
-#cmakedefine HAVE_OPEN
#cmakedefine HAVE_OPENSSL
#cmakedefine HAVE_SETMODE
#cmakedefine HAVE_SNPRINTF
