diff --git a/README.md b/README.md
index ed1302d8..3ffc0f1b 100644
--- a/README.md
+++ b/README.md
@@ -122,6 +122,13 @@ gmake repl
 3. Run `build_win` to compile janet.
 4. Run `build_win test` to make sure everything is working.
 
+To build an `.msi` installer executable, in addition to the above steps, you will have to:
+
+5. Install, or otherwise add to your PATH the [WiX 3.11 Toolset](https://github.com/wixtoolset/wix3/releases)
+6. run `build_win dist`
+
+Now you should have an `.msi`. You can run `build_win install` to install the `.msi`, or execute the file itself.
+
 ### Meson
 
 Janet also has a build file for [Meson](https://mesonbuild.com/), a cross platform build
diff --git a/examples/numarray/numarray.c b/examples/numarray/numarray.c
index ac411fad..0c3153a4 100644
--- a/examples/numarray/numarray.c
+++ b/examples/numarray/numarray.c
@@ -23,7 +23,7 @@ static int num_array_gc(void *p, size_t s) {
     return 0;
 }
 
-Janet num_array_get(void *p, Janet key);
+int num_array_get(void *p, Janet key, Janet *out); 
 void num_array_put(void *p, Janet key, Janet value);
 
 static const JanetAbstractType num_array_type = {
@@ -31,7 +31,8 @@ static const JanetAbstractType num_array_type = {
     num_array_gc,
     NULL,
     num_array_get,
-    num_array_put
+    num_array_put,
+    JANET_ATEND_PUT
 };
 
 static Janet num_array_new(int32_t argc, Janet *argv) {
@@ -81,21 +82,20 @@ static const JanetMethod methods[] = {
     {NULL, NULL}
 };
 
-Janet num_array_get(void *p, Janet key) {
+int num_array_get(void *p, Janet key, Janet *out) {
     size_t index;
-    Janet value;
     num_array *array = (num_array *)p;
     if (janet_checktype(key, JANET_KEYWORD))
-        return janet_getmethod(janet_unwrap_keyword(key), methods);
+        return janet_getmethod(janet_unwrap_keyword(key), methods, out);
     if (!janet_checkint(key))
         janet_panic("expected integer key");
     index = (size_t)janet_unwrap_integer(key);
     if (index >= array->size) {
-        value = janet_wrap_nil();
+        return 0;
     } else {
-        value = janet_wrap_number(array->data[index]);
+        *out = janet_wrap_number(array->data[index]);
     }
-    return value;
+    return 1;
 }
 
 static const JanetReg cfuns[] = {
diff --git a/examples/numarray/project.janet b/examples/numarray/project.janet
new file mode 100644
index 00000000..6cf5f327
--- /dev/null
+++ b/examples/numarray/project.janet
@@ -0,0 +1,7 @@
+(declare-project
+  :name "numarray"
+  :description "Example c lib with abstract type")
+
+(declare-native
+  :name "numarray"
+  :source @["numarray.c"])
diff --git a/examples/numarray/build.janet b/examples/numarray/test/numarray_tests.janet
similarity index 65%
rename from examples/numarray/build.janet
rename to examples/numarray/test/numarray_tests.janet
index 2e682568..5ae34bba 100644
--- a/examples/numarray/build.janet
+++ b/examples/numarray/test/numarray_tests.janet
@@ -1,10 +1,4 @@
-(import cook)
-
-(cook/make-native
-    :name "numarray"
-    :source @["numarray.c"])
-
-(import build/numarray :as numarray)
+(import build/numarray)
 
 (def a (numarray/new 30))
 (print (get a 20))
diff --git a/src/core/compile.c b/src/core/compile.c
index 88d9b7a3..dd802b3e 100644
--- a/src/core/compile.c
+++ b/src/core/compile.c
@@ -750,12 +750,14 @@ JanetFuncDef *janetc_pop_funcdef(JanetCompiler *c) {
     /* Copy upvalue bitset */
     if (scope->ua.count) {
         /* Number of u32s we need to create a bitmask for all slots */
-        int32_t numchunks = (def->slotcount + 31) >> 5;
-        uint32_t *chunks = calloc(sizeof(uint32_t), numchunks);
+        int32_t slotchunks = (def->slotcount + 31) >> 5;
+        /* numchunks is min of slotchunks and scope->ua.count */
+        int32_t numchunks = slotchunks > scope->ua.count ? scope->ua.count : slotchunks;
+        uint32_t *chunks = calloc(sizeof(uint32_t), slotchunks);
         if (NULL == chunks) {
             JANET_OUT_OF_MEMORY;
         }
-        memcpy(chunks, scope->ua.chunks, sizeof(uint32_t) * scope->ua.count);
+        memcpy(chunks, scope->ua.chunks, sizeof(uint32_t) * numchunks);
         /* Register allocator preallocates some registers [240-255, high 16 bits of chunk index 7], we can ignore those. */
         if (scope->ua.count > 7) chunks[7] &= 0xFFFFU;
         def->closure_bitset = chunks;