diff --git a/library/lms.c b/library/lms.c
index 8d3cae0..7f7bec0 100644
--- a/library/lms.c
+++ b/library/lms.c
@@ -229,6 +229,10 @@
 
 void mbedtls_lms_public_free(mbedtls_lms_public_t *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     mbedtls_platform_zeroize(ctx, sizeof(*ctx));
 }
 
@@ -528,6 +532,10 @@
 
 void mbedtls_lms_private_free(mbedtls_lms_private_t *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     unsigned int idx;
 
     if (ctx->have_private_key) {