diff --git a/crypto_kem/ntruhps2048509/META.yml b/crypto_kem/ntruhps2048509/META.yml
index 043d9686..6caa66fc 100644
--- a/crypto_kem/ntruhps2048509/META.yml
+++ b/crypto_kem/ntruhps2048509/META.yml
@@ -23,9 +23,9 @@ auxiliary-submitters:
   - Zhenfei Zhang
 implementations:
     - name: clean
-      version: https://github.com/jschanck/ntru/tree/00f73a7f reference implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 reference implementation
     - name: avx2
-      version: https://github.com/jschanck/ntru/tree/00f73a7f avx2 implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 avx2 implementation
       supported_platforms:
           - architecture: x86_64
             operating_systems:
diff --git a/crypto_kem/ntruhps2048509/clean/poly_s3_inv.c b/crypto_kem/ntruhps2048509/clean/poly_s3_inv.c
index 92b08480..67047f5c 100644
--- a/crypto_kem/ntruhps2048509/clean/poly_s3_inv.c
+++ b/crypto_kem/ntruhps2048509/clean/poly_s3_inv.c
@@ -44,7 +44,7 @@ void PQCLEAN_NTRUHPS2048509_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
         v.coeffs[0] = 0;
 
-        sign = mod3(2 * g.coeffs[0] * f.coeffs[0]);
+        sign = mod3((uint8_t) (2 * g.coeffs[0] * f.coeffs[0]));
         swap = both_negative_mask(-delta, -(int) g.coeffs[0]);
         delta ^= swap & (delta ^ -delta);
         delta += 1;
@@ -59,10 +59,10 @@ void PQCLEAN_NTRUHPS2048509_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
 
         for (i = 0; i < NTRU_N; ++i) {
-            g.coeffs[i] = mod3(g.coeffs[i] + sign * f.coeffs[i]);
+            g.coeffs[i] = mod3((uint8_t) (g.coeffs[i] + sign * f.coeffs[i]));
         }
         for (i = 0; i < NTRU_N; ++i) {
-            w.coeffs[i] = mod3(w.coeffs[i] + sign * v.coeffs[i]);
+            w.coeffs[i] = mod3((uint8_t) (w.coeffs[i] + sign * v.coeffs[i]));
         }
         for (i = 0; i < NTRU_N - 1; ++i) {
             g.coeffs[i] = g.coeffs[i + 1];
@@ -72,7 +72,7 @@ void PQCLEAN_NTRUHPS2048509_CLEAN_poly_S3_inv(poly *r, const poly *a) {
 
     sign = f.coeffs[0];
     for (i = 0; i < NTRU_N - 1; ++i) {
-        r->coeffs[i] = mod3(sign * v.coeffs[NTRU_N - 2 - i]);
+        r->coeffs[i] = mod3((uint8_t) (sign * v.coeffs[NTRU_N - 2 - i]));
     }
     r->coeffs[NTRU_N - 1] = 0;
 }
diff --git a/crypto_kem/ntruhps2048677/META.yml b/crypto_kem/ntruhps2048677/META.yml
index 8fbbd05f..197dfc60 100644
--- a/crypto_kem/ntruhps2048677/META.yml
+++ b/crypto_kem/ntruhps2048677/META.yml
@@ -23,9 +23,9 @@ auxiliary-submitters:
   - Zhenfei Zhang
 implementations:
     - name: clean
-      version: https://github.com/jschanck/ntru/tree/00f73a7f reference implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 reference implementation
     - name: avx2
-      version: https://github.com/jschanck/ntru/tree/00f73a7f avx2 implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 avx2 implementation
       supported_platforms:
           - architecture: x86_64
             operating_systems:
diff --git a/crypto_kem/ntruhps2048677/clean/poly_s3_inv.c b/crypto_kem/ntruhps2048677/clean/poly_s3_inv.c
index 3412f136..19466db0 100644
--- a/crypto_kem/ntruhps2048677/clean/poly_s3_inv.c
+++ b/crypto_kem/ntruhps2048677/clean/poly_s3_inv.c
@@ -44,7 +44,7 @@ void PQCLEAN_NTRUHPS2048677_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
         v.coeffs[0] = 0;
 
-        sign = mod3(2 * g.coeffs[0] * f.coeffs[0]);
+        sign = mod3((uint8_t) (2 * g.coeffs[0] * f.coeffs[0]));
         swap = both_negative_mask(-delta, -(int) g.coeffs[0]);
         delta ^= swap & (delta ^ -delta);
         delta += 1;
@@ -59,10 +59,10 @@ void PQCLEAN_NTRUHPS2048677_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
 
         for (i = 0; i < NTRU_N; ++i) {
-            g.coeffs[i] = mod3(g.coeffs[i] + sign * f.coeffs[i]);
+            g.coeffs[i] = mod3((uint8_t) (g.coeffs[i] + sign * f.coeffs[i]));
         }
         for (i = 0; i < NTRU_N; ++i) {
-            w.coeffs[i] = mod3(w.coeffs[i] + sign * v.coeffs[i]);
+            w.coeffs[i] = mod3((uint8_t) (w.coeffs[i] + sign * v.coeffs[i]));
         }
         for (i = 0; i < NTRU_N - 1; ++i) {
             g.coeffs[i] = g.coeffs[i + 1];
@@ -72,7 +72,7 @@ void PQCLEAN_NTRUHPS2048677_CLEAN_poly_S3_inv(poly *r, const poly *a) {
 
     sign = f.coeffs[0];
     for (i = 0; i < NTRU_N - 1; ++i) {
-        r->coeffs[i] = mod3(sign * v.coeffs[NTRU_N - 2 - i]);
+        r->coeffs[i] = mod3((uint8_t) (sign * v.coeffs[NTRU_N - 2 - i]));
     }
     r->coeffs[NTRU_N - 1] = 0;
 }
diff --git a/crypto_kem/ntruhps4096821/META.yml b/crypto_kem/ntruhps4096821/META.yml
index 9da1e89b..a9ea40b3 100644
--- a/crypto_kem/ntruhps4096821/META.yml
+++ b/crypto_kem/ntruhps4096821/META.yml
@@ -23,9 +23,9 @@ auxiliary-submitters:
   - Zhenfei Zhang
 implementations:
     - name: clean
-      version: https://github.com/jschanck/ntru/tree/00f73a7f reference implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 reference implementation
     - name: avx2
-      version: https://github.com/jschanck/ntru/tree/00f73a7f avx2 implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 avx2 implementation
       supported_platforms:
           - architecture: x86_64
             operating_systems:
diff --git a/crypto_kem/ntruhps4096821/clean/poly_s3_inv.c b/crypto_kem/ntruhps4096821/clean/poly_s3_inv.c
index 0f6ec95c..0cd00e97 100644
--- a/crypto_kem/ntruhps4096821/clean/poly_s3_inv.c
+++ b/crypto_kem/ntruhps4096821/clean/poly_s3_inv.c
@@ -44,7 +44,7 @@ void PQCLEAN_NTRUHPS4096821_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
         v.coeffs[0] = 0;
 
-        sign = mod3(2 * g.coeffs[0] * f.coeffs[0]);
+        sign = mod3((uint8_t) (2 * g.coeffs[0] * f.coeffs[0]));
         swap = both_negative_mask(-delta, -(int) g.coeffs[0]);
         delta ^= swap & (delta ^ -delta);
         delta += 1;
@@ -59,10 +59,10 @@ void PQCLEAN_NTRUHPS4096821_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
 
         for (i = 0; i < NTRU_N; ++i) {
-            g.coeffs[i] = mod3(g.coeffs[i] + sign * f.coeffs[i]);
+            g.coeffs[i] = mod3((uint8_t) (g.coeffs[i] + sign * f.coeffs[i]));
         }
         for (i = 0; i < NTRU_N; ++i) {
-            w.coeffs[i] = mod3(w.coeffs[i] + sign * v.coeffs[i]);
+            w.coeffs[i] = mod3((uint8_t) (w.coeffs[i] + sign * v.coeffs[i]));
         }
         for (i = 0; i < NTRU_N - 1; ++i) {
             g.coeffs[i] = g.coeffs[i + 1];
@@ -72,7 +72,7 @@ void PQCLEAN_NTRUHPS4096821_CLEAN_poly_S3_inv(poly *r, const poly *a) {
 
     sign = f.coeffs[0];
     for (i = 0; i < NTRU_N - 1; ++i) {
-        r->coeffs[i] = mod3(sign * v.coeffs[NTRU_N - 2 - i]);
+        r->coeffs[i] = mod3((uint8_t) (sign * v.coeffs[NTRU_N - 2 - i]));
     }
     r->coeffs[NTRU_N - 1] = 0;
 }
diff --git a/crypto_kem/ntruhrss701/META.yml b/crypto_kem/ntruhrss701/META.yml
index 36617929..de3c690a 100644
--- a/crypto_kem/ntruhrss701/META.yml
+++ b/crypto_kem/ntruhrss701/META.yml
@@ -23,9 +23,9 @@ auxiliary-submitters:
   - Zhenfei Zhang
 implementations:
     - name: clean
-      version: https://github.com/jschanck/ntru/tree/00f73a7f reference implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 reference implementation
     - name: avx2
-      version: https://github.com/jschanck/ntru/tree/00f73a7f avx2 implementation
+      version: https://github.com/jschanck/ntru/tree/ba431bb8 avx2 implementation
       supported_platforms:
           - architecture: x86_64
             operating_systems:
diff --git a/crypto_kem/ntruhrss701/clean/poly_s3_inv.c b/crypto_kem/ntruhrss701/clean/poly_s3_inv.c
index 6100a08f..fd672ca2 100644
--- a/crypto_kem/ntruhrss701/clean/poly_s3_inv.c
+++ b/crypto_kem/ntruhrss701/clean/poly_s3_inv.c
@@ -44,7 +44,7 @@ void PQCLEAN_NTRUHRSS701_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
         v.coeffs[0] = 0;
 
-        sign = mod3(2 * g.coeffs[0] * f.coeffs[0]);
+        sign = mod3((uint8_t) (2 * g.coeffs[0] * f.coeffs[0]));
         swap = both_negative_mask(-delta, -(int) g.coeffs[0]);
         delta ^= swap & (delta ^ -delta);
         delta += 1;
@@ -59,10 +59,10 @@ void PQCLEAN_NTRUHRSS701_CLEAN_poly_S3_inv(poly *r, const poly *a) {
         }
 
         for (i = 0; i < NTRU_N; ++i) {
-            g.coeffs[i] = mod3(g.coeffs[i] + sign * f.coeffs[i]);
+            g.coeffs[i] = mod3((uint8_t) (g.coeffs[i] + sign * f.coeffs[i]));
         }
         for (i = 0; i < NTRU_N; ++i) {
-            w.coeffs[i] = mod3(w.coeffs[i] + sign * v.coeffs[i]);
+            w.coeffs[i] = mod3((uint8_t) (w.coeffs[i] + sign * v.coeffs[i]));
         }
         for (i = 0; i < NTRU_N - 1; ++i) {
             g.coeffs[i] = g.coeffs[i + 1];
@@ -72,7 +72,7 @@ void PQCLEAN_NTRUHRSS701_CLEAN_poly_S3_inv(poly *r, const poly *a) {
 
     sign = f.coeffs[0];
     for (i = 0; i < NTRU_N - 1; ++i) {
-        r->coeffs[i] = mod3(sign * v.coeffs[NTRU_N - 2 - i]);
+        r->coeffs[i] = mod3((uint8_t) (sign * v.coeffs[NTRU_N - 2 - i]));
     }
     r->coeffs[NTRU_N - 1] = 0;
 }