diff --git a/defs.h b/defs.h
index f9af7c89..3ba43c4f 100644
--- a/defs.h
+++ b/defs.h
@@ -184,6 +184,8 @@ typedef struct PacketProtocolLayer PacketProtocolLayer;
 
 #if defined __GNUC__ || defined __clang__
 #define NORETURN __attribute__((__noreturn__))
+#elif defined _MSC_VER
+#define NORETURN __declspec(noreturn)
 #else
 #define NORETURN
 #endif
diff --git a/mpint.c b/mpint.c
index 2454a755..39f55063 100644
--- a/mpint.c
+++ b/mpint.c
@@ -1183,7 +1183,7 @@ static void mp_rshift_safe_in_place(mp_int *r, size_t bits)
     mp_cond_clear(r, clear);
 
     for (unsigned bit = 0; r->nw >> bit; bit++) {
-        size_t word_offset = 1 << bit;
+        size_t word_offset = (size_t)1 << bit;
         BignumInt mask = -(BignumInt)((wordshift >> bit) & 1);
         for (size_t i = 0; i < r->nw; i++) {
             BignumInt w = mp_word(r, i + word_offset);
@@ -1232,7 +1232,7 @@ static void mp_lshift_safe_in_place(mp_int *r, size_t bits)
     mp_cond_clear(r, clear);
 
     for (unsigned bit = 0; r->nw >> bit; bit++) {
-        size_t word_offset = 1 << bit;
+        size_t word_offset = (size_t)1 << bit;
         BignumInt mask = -(BignumInt)((wordshift >> bit) & 1);
         for (size_t i = r->nw; i-- > 0 ;) {
             BignumInt w = mp_word(r, i - word_offset);
@@ -2042,7 +2042,7 @@ void mp_divmod_into(mp_int *n, mp_int *d, mp_int *q_out, mp_int *r_out)
      */
     size_t shift_up = 0;
     for (size_t i = BIGNUM_INT_BITS_BITS; i-- > 0;) {
-        size_t sl = 1 << i;               /* left shift count */
+        size_t sl = (size_t)1 << i;       /* left shift count */
         size_t sr = 64 - sl;     /* complementary right-shift count */
 
         /* Should we shift up? */
@@ -2079,7 +2079,7 @@ void mp_divmod_into(mp_int *n, mp_int *d, mp_int *q_out, mp_int *r_out)
      * instructions, e.g. by splitting up into cases.
      */
     for (size_t i = BIGNUM_INT_BITS_BITS; i-- > 0;) {
-        size_t sl = 1 << i;               /* left shift count */
+        size_t sl = (size_t)1 << i;       /* left shift count */
         size_t sr = 64 - sl;     /* complementary right-shift count */
 
         /* Should we shift up? */
diff --git a/sshzlib.c b/sshzlib.c
index 015afba1..9ad04ed2 100644
--- a/sshzlib.c
+++ b/sshzlib.c
@@ -730,7 +730,7 @@ static struct zlib_table *zlib_mkonetab(int *codes, unsigned char *lengths,
     int pfxmask = (1 << pfxbits) - 1;
     int nbits, i, j, code;
 
-    tab->table = snewn(1 << bits, struct zlib_tableentry);
+    tab->table = snewn((size_t)1 << bits, struct zlib_tableentry);
     tab->mask = (1 << bits) - 1;
 
     for (code = 0; code <= tab->mask; code++) {