diff --git a/crypto_kem/sntrup653/clean/crypto_core_invsntrup653.c b/crypto_kem/sntrup653/clean/crypto_core_invsntrup653.c
index 572abb39..98705b0f 100644
--- a/crypto_kem/sntrup653/clean/crypto_core_invsntrup653.c
+++ b/crypto_kem/sntrup653/clean/crypto_core_invsntrup653.c
@@ -15,7 +15,7 @@
 static int int16_nonzero_mask(int16 x) {
     uint16 u = (uint16) x; /* 0, else 1...65535 */
     uint32 v = u; /* 0, else 1...65535 */
-    v = -v; /* 0, else 2^32-65535...2^32-1 */
+    v = ~v + 1; /* 0, else 2^32-65535...2^32-1 */
     v >>= 31; /* 0, else 1 */
     return -(int) v; /* 0, else -1 */
 }
diff --git a/crypto_kem/sntrup761/clean/crypto_core_invsntrup761.c b/crypto_kem/sntrup761/clean/crypto_core_invsntrup761.c
index 16afe697..dab970d4 100644
--- a/crypto_kem/sntrup761/clean/crypto_core_invsntrup761.c
+++ b/crypto_kem/sntrup761/clean/crypto_core_invsntrup761.c
@@ -15,7 +15,7 @@
 static int int16_nonzero_mask(int16 x) {
     uint16 u = (uint16) x; /* 0, else 1...65535 */
     uint32 v = u; /* 0, else 1...65535 */
-    v = -v; /* 0, else 2^32-65535...2^32-1 */
+    v = ~v + 1; /* 0, else 2^32-65535...2^32-1 */
     v >>= 31; /* 0, else 1 */
     return -(int) v; /* 0, else -1 */
 }
diff --git a/crypto_kem/sntrup857/clean/crypto_core_invsntrup857.c b/crypto_kem/sntrup857/clean/crypto_core_invsntrup857.c
index 383f2951..a8737a97 100644
--- a/crypto_kem/sntrup857/clean/crypto_core_invsntrup857.c
+++ b/crypto_kem/sntrup857/clean/crypto_core_invsntrup857.c
@@ -15,7 +15,7 @@
 static int int16_nonzero_mask(int16 x) {
     uint16 u = (uint16) x; /* 0, else 1...65535 */
     uint32 v = u; /* 0, else 1...65535 */
-    v = -v; /* 0, else 2^32-65535...2^32-1 */
+    v = ~v + 1; /* 0, else 2^32-65535...2^32-1 */
     v >>= 31; /* 0, else 1 */
     return -(int) v; /* 0, else -1 */
 }