diff --git a/knot/Implementations/crypto_aead/knot128v1/armcortexm_3/encrypt.c b/knot/Implementations/crypto_aead/knot128v1/armcortexm_3/encrypt.c
index 30c6c80..5a0052d 100644
--- a/knot/Implementations/crypto_aead/knot128v1/armcortexm_3/encrypt.c
+++ b/knot/Implementations/crypto_aead/knot128v1/armcortexm_3/encrypt.c
@@ -237,8 +237,8 @@ int crypto_aead_decrypt(unsigned char *m, unsigned long long *mlen,
 		unpackFormat(tempU8, s);
 		unpackFormat((tempU8+8), (s+2));
 	if (memcmp((void*)tempU8, (void*)c,CRYPTO_ABYTES)) {
+		memset(m, 0, sizeof(unsigned char) * (*mlen));
 		*mlen = 0;
-		memset(m, 0, sizeof(unsigned char) * (clen - CRYPTO_ABYTES));
 	   return -1;
 	}
 	return 0;
diff --git a/knot/Implementations/crypto_aead/knot128v2/armcortexm_3/encrypt.c b/knot/Implementations/crypto_aead/knot128v2/armcortexm_3/encrypt.c
index 28abf55..0315084 100644
--- a/knot/Implementations/crypto_aead/knot128v2/armcortexm_3/encrypt.c
+++ b/knot/Implementations/crypto_aead/knot128v2/armcortexm_3/encrypt.c
@@ -248,8 +248,8 @@ int crypto_aead_decrypt(unsigned char *m, unsigned long long *mlen,
 	unpackU96FormatToThreePacket(tempU8, s);
 	unpackU96FormatToThreePacket((tempU8 + 12), (s + 3));
 	if (memcmp((void*)tempU8, (void*)c, CRYPTO_ABYTES)) {
+		memset(m, 0, sizeof(unsigned char) * (*mlen));
 		*mlen = 0;
-		memset(m, 0, sizeof(unsigned char) * (clen - CRYPTO_ABYTES));
 		return -1;
 	}
 	return 0;
diff --git a/knot/Implementations/crypto_aead/knot192/armcortexm_3/encrypt.c b/knot/Implementations/crypto_aead/knot192/armcortexm_3/encrypt.c
index 9513625..65c8859 100644
--- a/knot/Implementations/crypto_aead/knot192/armcortexm_3/encrypt.c
+++ b/knot/Implementations/crypto_aead/knot192/armcortexm_3/encrypt.c
@@ -202,8 +202,8 @@ int crypto_aead_decrypt(unsigned char *m, unsigned long long *mlen,
 	unpackU96FormatToThreePacket(tempU8, s);
 	unpackU96FormatToThreePacket((tempU8 + 12), (s + 3));
 	if (memcmp((void*)tempU8, (void*)c, CRYPTO_ABYTES)) {
+		memset(m, 0, sizeof(unsigned char) * (*mlen));
 		*mlen = 0;
-		memset(m, 0, sizeof(unsigned char) * (clen - CRYPTO_ABYTES));
 		return -1;
 	}
 	return 0;
diff --git a/knot/Implementations/crypto_aead/knot256/armcortexm_3/encrypt.c b/knot/Implementations/crypto_aead/knot256/armcortexm_3/encrypt.c
index d8d1476..3fc96ee 100644
--- a/knot/Implementations/crypto_aead/knot256/armcortexm_3/encrypt.c
+++ b/knot/Implementations/crypto_aead/knot256/armcortexm_3/encrypt.c
@@ -320,9 +320,9 @@ int crypto_aead_decrypt(
 	unpackU128FormatToFourPacket(tempU8, s);
 	unpackU128FormatToFourPacket((tempU8 + 16), (s + 4));
 	if (memcmp((void*)tempU8, (void*)c, CRYPTO_ABYTES)) {
+		memset(m, 0, sizeof(unsigned char) * (*mlen));
 		*mlen = 0;
-		memset(m, 0, sizeof(unsigned char) * (clen - CRYPTO_ABYTES));
 		return -1;
 	}
 	return 0;
-}
\ No newline at end of file
+}