diff --git a/ChangeLog b/ChangeLog
index d84a364f8..f2dc2e7b6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -8,6 +8,14 @@ Security
      blinded value, factor it (as it is smaller than RSA keys and not guaranteed
      to have only large prime factors), and then, by brute force, recover the
      key. Reported by Alejandro Cabrera Aldaya and Billy Brumley.
+   * Zeroize local variables in mbedtls_internal_aes_encrypt() and
+     mbedtls_internal_aes_decrypt() before exiting the function. The value of
+     these variables can be used to recover the last round key. To follow best
+     practice and to limit the impact of buffer overread vulnerabilities (like
+     Heartbleed) we need to zeroize them before exiting the function.
+     Issue reported by Tuba Yavuz, Farhaan Fowze, Ken (Yihang) Bai,
+     Grant Hernandez, and Kevin Butler (University of Florida) and
+     Dave Tian (Purdue University).
 
 Changes
    * Add unit tests for AES-GCM when called through mbedtls_cipher_auth_xxx()
diff --git a/library/aes.c b/library/aes.c
index 3d2eac82d..beeecae37 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -761,6 +761,18 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx,
     PUT_UINT32_LE( X2, output,  8 );
     PUT_UINT32_LE( X3, output, 12 );
 
+    mbedtls_zeroize( &X0, sizeof( X0 ) );
+    mbedtls_zeroize( &X1, sizeof( X1 ) );
+    mbedtls_zeroize( &X2, sizeof( X2 ) );
+    mbedtls_zeroize( &X3, sizeof( X3 ) );
+
+    mbedtls_zeroize( &Y0, sizeof( Y0 ) );
+    mbedtls_zeroize( &Y1, sizeof( Y1 ) );
+    mbedtls_zeroize( &Y2, sizeof( Y2 ) );
+    mbedtls_zeroize( &Y3, sizeof( Y3 ) );
+
+    mbedtls_zeroize( &RK, sizeof( RK ) );
+
     return( 0 );
 }
 #endif /* !MBEDTLS_AES_ENCRYPT_ALT */
@@ -829,6 +841,18 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx,
     PUT_UINT32_LE( X2, output,  8 );
     PUT_UINT32_LE( X3, output, 12 );
 
+    mbedtls_zeroize( &X0, sizeof( X0 ) );
+    mbedtls_zeroize( &X1, sizeof( X1 ) );
+    mbedtls_zeroize( &X2, sizeof( X2 ) );
+    mbedtls_zeroize( &X3, sizeof( X3 ) );
+
+    mbedtls_zeroize( &Y0, sizeof( Y0 ) );
+    mbedtls_zeroize( &Y1, sizeof( Y1 ) );
+    mbedtls_zeroize( &Y2, sizeof( Y2 ) );
+    mbedtls_zeroize( &Y3, sizeof( Y3 ) );
+
+    mbedtls_zeroize( &RK, sizeof( RK ) );
+
     return( 0 );
 }
 #endif /* !MBEDTLS_AES_DECRYPT_ALT */