diff --git a/CMakeLists.txt b/CMakeLists.txt
index ced0e2683c..03dc130686 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1560,8 +1560,9 @@ _add_if("HTTPS-proxy"   SSL_ENABLED AND (USE_OPENSSL OR USE_GNUTLS
                         OR USE_SCHANNEL OR USE_RUSTLS OR USE_BEARSSL OR
                         USE_MBEDTLS OR USE_SECTRANSP))
 _add_if("unicode"       ENABLE_UNICODE)
-_add_if("threadsafe"    HAVE_ATOMIC OR (WIN32 AND
-                        HAVE_WIN32_WINNT GREATER_EQUAL 0x600))
+_add_if("threadsafe"    HAVE_ATOMIC OR
+                        (USE_THREADS_POSIX AND HAVE_PTHREAD_H) OR
+                        (WIN32 AND HAVE_WIN32_WINNT GREATER_EQUAL 0x600))
 _add_if("PSL"           USE_LIBPSL)
 string(REPLACE ";" " " SUPPORT_FEATURES "${_items}")
 message(STATUS "Enabled features: ${SUPPORT_FEATURES}")
diff --git a/configure.ac b/configure.ac
index 2d71c838f8..1861e1e59f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4612,6 +4612,9 @@ fi
 
 if test "$tst_atomic" = "yes"; then
   SUPPORT_FEATURES="$SUPPORT_FEATURES threadsafe"
+elif test "x$USE_THREADS_POSIX" = "x1" -a \
+     "x$ac_cv_header_pthread_h" = "xyes"; then
+  SUPPORT_FEATURES="$SUPPORT_FEATURES threadsafe"
 else
   AC_COMPILE_IFELSE([
     AC_LANG_PROGRAM([[