diff --git a/DESCRIPTION b/DESCRIPTION
index 2e297a4..dc35217 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -10,7 +10,7 @@ Authors@R: c(
            comment = "Author of QuickJS sources and headers")
   )
 Description: An 'R' interface to the 'QuickJS' portable 'JavaScript'
-    engine.  The engine and all 'R' to 'JavaScript' operability is bundled
+    engine.  The engine and all 'R' to 'JavaScript' interopability is bundled
     within the package, requiring no dependencies beyond a 'C' compiler.
 License: MIT + file LICENSE
 URL: https://github.com/andrjohns/QuickJSR, https://bellard.org/quickjs/
diff --git a/NEWS.md b/NEWS.md
index efa0d29..6134f8b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,10 @@
+# QuickJSR 1.2.0
+  - `Rcpp` dependency replaced with vendored `cpp11` headers
+  - `R6` dependency removed
+  - `R` and `JS` interopability added, removing `jsonlite` dependency
+  - Fixes for libatomic linking on 32-bit systems
+  - Added `to_json` and `from_json` functions for testing `R`/`JS` interop
+
 # QuickJSR 1.1.0
   - Fixed UBSAN error in `JS_Eval`
   - Fixed compilation errors with older GCC & Clang (`stdatomic.h not found`)
diff --git a/inst/include/quickjsr/JSCommonType.hpp b/inst/include/quickjsr/JSCommonType.hpp
index 1adfdee..1ff48f8 100644
--- a/inst/include/quickjsr/JSCommonType.hpp
+++ b/inst/include/quickjsr/JSCommonType.hpp
@@ -14,12 +14,16 @@ enum JSCommonType {
   Date,
   NumberArray,
   Object,
+  Undefined,
   Unknown
 };
 
 JSCommonType JS_ArrayCommonType(JSContext* ctx, const JSValue& val);
 
 JSCommonType JS_GetCommonType(JSContext* ctx, const JSValue& val) {
+  if (JS_IsUndefined(val)) {
+    return Undefined;
+  }
   if (JS_IsBool(val)) {
     return Logical;
   }
@@ -32,6 +36,9 @@ JSCommonType JS_GetCommonType(JSContext* ctx, const JSValue& val) {
   if (JS_IsString(val)) {
     return Character;
   }
+  if (JS_IsObject(val)) {
+    return Object;
+  }
   if (JS_IsDate(ctx, val)) {
     return Date;
   }
@@ -41,9 +48,6 @@ JSCommonType JS_GetCommonType(JSContext* ctx, const JSValue& val) {
       return NumberArray;
     }
   }
-  if (JS_IsObject(val)) {
-    return Object;
-  }
   return Unknown;
 }
 
@@ -56,6 +60,9 @@ JSCommonType JS_UpdateCommonType(JSCommonType current, JSContext* ctx, const JSV
   if (current == new_type) {
     return current;
   }
+  if (new_type == Undefined) {
+    return current;
+  }
   // If one, but not both, types are NumberArray or Date (checked above), return Object
   if (new_type == NumberArray || current == NumberArray || new_type == Object
       || new_type == Date || current == Date) {
diff --git a/inst/include/quickjsr/JSValue_Date.hpp b/inst/include/quickjsr/JSValue_Date.hpp
index 19da2e2..29e48ff 100644
--- a/inst/include/quickjsr/JSValue_Date.hpp
+++ b/inst/include/quickjsr/JSValue_Date.hpp
@@ -4,6 +4,7 @@
 #include <cpp11.hpp>
 #include <quickjs-libc.h>
 #include <cstring>
+#include <iostream>
 
 namespace quickjsr {
 
@@ -15,6 +16,10 @@ inline double get_tz_offset_seconds() {
 
 inline bool JS_IsDate(JSContext* ctx, const JSValue& val) {
   JSValue ctor = JS_GetPropertyStr(ctx, val, "constructor");
+  if (JS_IsException(ctor)) {
+    JS_FreeValue(ctx, ctor);
+    return false;
+  }
   JSValue ctorName = JS_GetPropertyStr(ctx, ctor, "name");
 
   const char* name = JS_ToCString(ctx, ctorName);
diff --git a/inst/include/quickjsr/JSValue_to_SEXP.hpp b/inst/include/quickjsr/JSValue_to_SEXP.hpp
index 09b383d..25765f9 100644
--- a/inst/include/quickjsr/JSValue_to_SEXP.hpp
+++ b/inst/include/quickjsr/JSValue_to_SEXP.hpp
@@ -24,6 +24,9 @@ static void js_free_prop_enum(JSContext *ctx, JSPropertyEnum *tab, uint32_t len)
 SEXP JSValue_to_SEXP(JSContext* ctx, const JSValue& val);
 
 SEXP JSValue_to_SEXP_scalar(JSContext* ctx, const JSValue& val) {
+  if (JS_IsUndefined(val)) {
+    return R_NilValue;
+  }
   if (JS_IsBool(val)) {
     return cpp11::as_sexp(JSValue_to_Cpp<bool>(ctx, val));
   }
@@ -54,6 +57,8 @@ SEXP JSValue_to_SEXP_vector(JSContext* ctx, const JSValue& val) {
       return cpp11::as_sexp(JSValue_to_Cpp<std::vector<bool>>(ctx, val));
     case Character:
       return cpp11::as_sexp(JSValue_to_Cpp<std::vector<std::string>>(ctx, val));
+    case Undefined:
+      return R_NilValue;
     case Date: {
       cpp11::writable::doubles res = cpp11::as_sexp(JSValue_to_Cpp<std::vector<double>>(ctx, val));
       res.attr("class") = "POSIXct";
@@ -95,8 +100,14 @@ SEXP JSValue_to_SEXP_vector(JSContext* ctx, const JSValue& val) {
       }
       return out;
     }
-    default:
-      return cpp11::as_sexp("Unsupported type");
+    default: {
+      std::string type_str = "Unsupported type: ";
+      // Get result of typeof
+      JSValue typeof_val = JS_GetPropertyStr(ctx, val, "typeof");
+      type_str += JSValue_to_Cpp<std::string>(ctx, typeof_val);
+      JS_FreeValue(ctx, typeof_val);
+      return cpp11::as_sexp(type_str.c_str());
+    }
   }
 }
 
@@ -123,6 +134,9 @@ SEXP JSValue_to_SEXP_list(JSContext* ctx, const JSValue& val) {
 }
 
 SEXP JSValue_to_SEXP(JSContext* ctx, const JSValue& val) {
+  if (JS_IsUndefined(val)) {
+    return R_NilValue;
+  }
   if (JS_IsArray(ctx, val)) {
     return JSValue_to_SEXP_vector(ctx, val);
   }
diff --git a/src/quickjsr.cpp b/src/quickjsr.cpp
index 251f2cf..7dff563 100644
--- a/src/quickjsr.cpp
+++ b/src/quickjsr.cpp
@@ -24,8 +24,9 @@ extern "C" SEXP qjs_context_(SEXP stack_size_) {
   int stack_size = cpp11::as_cpp<int>(stack_size_);
 
   RuntimeXPtr rt(JS_NewRuntime());
+  // Workaround for RStan stack overflow until they update
   if (stack_size != -1) {
-    JS_SetMaxStackSize(rt.get(), stack_size);
+    JS_SetMaxStackSize(rt.get(), 0);
   }
   js_std_init_handlers(rt.get());
   ContextXPtr ctx(JS_NewContext(rt.get()));