diff --git a/ChangeLog.d/replace_time_t.txt b/ChangeLog.d/replace_time_t.txt
new file mode 100644
index 0000000000..ec0282a9f2
--- /dev/null
+++ b/ChangeLog.d/replace_time_t.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fix a build error or incorrect TLS session
+     lifetime on platforms where mbedtls_time_t
+     is not time_t. Fixes #10236.
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 37e4259e55..75c59a96ad 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3178,7 +3178,7 @@ static int ssl_tls12_session_load(mbedtls_ssl_session *session,
     start = MBEDTLS_GET_UINT64_BE(p, 0);
     p += 8;
 
-    session->start = (time_t) start;
+    session->start = (mbedtls_time_t) start;
 #endif /* MBEDTLS_HAVE_TIME */
 
     /*
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 1c52990a8e..efa003da0d 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -25,7 +25,6 @@
 #if defined(MBEDTLS_HAVE_TIME)
 #include <time.h>
 #define mbedtls_time            time
-#define mbedtls_time_t          time_t
 #endif
 #define mbedtls_printf          printf
 #define mbedtls_calloc          calloc