diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index d3ddbcc..0d6f6bb 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -43,6 +43,10 @@
 
 void mbedtls_x509write_csr_free(mbedtls_x509write_csr *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     mbedtls_asn1_free_named_data_list(&ctx->subject);
     mbedtls_asn1_free_named_data_list(&ctx->extensions);