diff --git a/LOG b/LOG
index b3b1dfaa5b..559e4e65a0 100644
--- a/LOG
+++ b/LOG
@@ -253,3 +253,6 @@
   concurrently. Updated $yield and $thread-check in mats/thread.ms to
   be more tolerant of timing variability.
     c/types.h, mats/thread.ms, release_notes.stex
+- fixed three instances of unchecked mallocs reported by laqrix in
+  github issue #77.
+    io.c, schlib.c, thread.c
diff --git a/c/io.c b/c/io.c
index 9de2449711..475b6c4547 100644
--- a/c/io.c
+++ b/c/io.c
@@ -84,7 +84,7 @@ char *S_malloc_pathname(const char *inpath) {
   /* if no ~ or tilde dir can't be found, copy inpath */
   {
     size_t n = strlen(inpath) + 1;
-    outpath = (char *)malloc(n);
+    if ((outpath = (char *)malloc(n)) == NULL) S_error("expand_pathname", "malloc failed");
     memcpy(outpath, inpath, n);
     return outpath;
   }
diff --git a/c/schlib.c b/c/schlib.c
index 9cdccaab45..9d7c6f7b97 100644
--- a/c/schlib.c
+++ b/c/schlib.c
@@ -217,6 +217,8 @@ void S_call_help(tc, singlep) ptr tc; IBOOL singlep; {
     CP(tc) = AC1(tc);
 
     jb = CREATEJMPBUF();
+    if (jb == NULL)
+      S_error_abort("unable to allocate memory for jump buffer");
     FRAME(tc, -1) = CCHAIN(tc) = Scons(Scons(jb, code), CCHAIN(tc));
 
     switch (SETJMP(jb)) {
diff --git a/c/thread.c b/c/thread.c
index 8206454987..0ca73c8dcf 100644
--- a/c/thread.c
+++ b/c/thread.c
@@ -63,6 +63,8 @@ ptr S_create_thread_object() {
     ptr v = S_vector_in(space_new, 0, n);
 
     tc = (ptr)malloc(size_tc);
+    if (tc == (ptr)0)
+      S_error("fork-thread", "unable to malloc thread data structure");
     memcpy((void *)tc, (void *)p_tc, size_tc);
 
     for (i = 0; i < n; i += 1)