diff --git a/lib/chibi/ast.c b/lib/chibi/ast.c
index 8e3cfed5..eed91898 100644
--- a/lib/chibi/ast.c
+++ b/lib/chibi/ast.c
@@ -409,9 +409,9 @@ static sexp sexp_gc_op (sexp ctx, sexp self, sexp_sint_t n) {
 }
 
 #if SEXP_USE_GREEN_THREADS
-static sexp sexp_set_atomic (sexp ctx, sexp self, sexp_sint_t n, sexp new) {
+static sexp sexp_set_atomic (sexp ctx, sexp self, sexp_sint_t n, sexp new_val) {
   sexp res = sexp_global(ctx, SEXP_G_ATOMIC_P);
-  sexp_global(ctx, SEXP_G_ATOMIC_P) = new;
+  sexp_global(ctx, SEXP_G_ATOMIC_P) = new_val;
   return res;
 }
 #endif
diff --git a/lib/chibi/disasm.c b/lib/chibi/disasm.c
index a364266a..bca944a9 100644
--- a/lib/chibi/disasm.c
+++ b/lib/chibi/disasm.c
@@ -74,7 +74,7 @@ static sexp disasm (sexp ctx, sexp self, sexp bc, sexp out, int depth) {
   sexp_newline(ctx, out);
 
   /* build a table of labels that are jumped to */
-  labels = calloc(sexp_bytecode_length(bc), sizeof(sexp_sint_t));
+  labels = (sexp_sint_t*)calloc(sexp_bytecode_length(bc), sizeof(sexp_sint_t));
   ip = sexp_bytecode_data(bc);
   while (ip - sexp_bytecode_data(bc) < sexp_bytecode_length(bc)) {
     switch (*ip++) {
diff --git a/lib/srfi/18/threads.c b/lib/srfi/18/threads.c
index 2858273e..5e943c02 100644
--- a/lib/srfi/18/threads.c
+++ b/lib/srfi/18/threads.c
@@ -352,7 +352,7 @@ static sexp sexp_get_signal_handler (sexp ctx, sexp self, sexp_sint_t n, sexp si
 
 static sexp sexp_make_pollfds (sexp ctx) {
   sexp res = sexp_alloc_tagged(ctx, sexp_sizeof_pollfds, sexp_unbox_fixnum(sexp_global(ctx, SEXP_G_THREADS_POLLFDS_ID)));
-  sexp_pollfds_fds(res) = malloc(SEXP_INIT_POLLFDS_MAX_FDS * sizeof(struct pollfd));
+  sexp_pollfds_fds(res) = (struct pollfd*)malloc(SEXP_INIT_POLLFDS_MAX_FDS * sizeof(struct pollfd));
   sexp_pollfds_num_fds(res) = 0;
   sexp_pollfds_max_fds(res) = SEXP_INIT_POLLFDS_MAX_FDS;
   return res;
@@ -385,7 +385,7 @@ static sexp sexp_insert_pollfd (sexp ctx, int fd, int events) {
   if (sexp_pollfds_num_fds(pollfds) == sexp_pollfds_max_fds(pollfds)) {
     sexp_pollfds_max_fds(pollfds) = i*2;
     pfd = sexp_pollfds_fds(pollfds);
-    sexp_pollfds_fds(pollfds) = malloc(i*2*sizeof(struct pollfd));
+    sexp_pollfds_fds(pollfds) = (struct pollfd*)malloc(i*2*sizeof(struct pollfd));
     if (sexp_pollfds_fds(pollfds))
       memcpy(sexp_pollfds_fds(pollfds), pfd, i*2*sizeof(struct pollfd));
     free(pfd);