diff --git a/library/md4.c b/library/md4.c
index 6982559..28e81c8 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -247,6 +247,13 @@
     ctx->state[2] += C;
     ctx->state[3] += D;
 
+    /* Zeroise variables to clear sensitive data from memory. */
+    mbedtls_zeroize( &X, sizeof( X ) );
+    mbedtls_zeroize( &A, sizeof( A ) );
+    mbedtls_zeroize( &B, sizeof( B ) );
+    mbedtls_zeroize( &C, sizeof( C ) );
+    mbedtls_zeroize( &D, sizeof( D ) );
+
     return( 0 );
 }