diff --git a/library/lmots.c b/library/lmots.c
index c7091b4..c51cb41 100644
--- a/library/lmots.c
+++ b/library/lmots.c
@@ -387,6 +387,10 @@
 
 void mbedtls_lmots_public_free(mbedtls_lmots_public_t *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     mbedtls_platform_zeroize(ctx, sizeof(*ctx));
 }
 
@@ -556,6 +560,10 @@
 
 void mbedtls_lmots_private_free(mbedtls_lmots_private_t *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     mbedtls_platform_zeroize(ctx,
                              sizeof(*ctx));
 }