diff --git a/src/runtime/lean.h b/src/runtime/lean.h
index 6b37fd91ab..b1e657b0fa 100644
--- a/src/runtime/lean.h
+++ b/src/runtime/lean.h
@@ -1434,12 +1434,22 @@ static inline bool lean_int_lt(b_lean_obj_arg a1, b_lean_obj_arg a2) {
     }
 }
 
+lean_obj_res lean_big_int_to_nat(lean_obj_arg a);
+static inline lean_obj_res lean_int_to_nat(lean_obj_arg a) {
+    assert(!lean_int_lt(a, lean_box(0)));
+    if (lean_is_scalar(a)) {
+        return a;
+    } else {
+        return lean_big_int_to_nat(a);
+    }
+}
+
 static inline lean_obj_res lean_nat_abs(b_lean_obj_arg i) {
     if (lean_int_lt(i, lean_box(0))) {
-        return lean_int_neg(i);
+        return lean_int_to_nat(lean_int_neg(i));
     } else {
         lean_inc(i);
-        return i;
+        return lean_int_to_nat(i);
     }
 }
 
diff --git a/src/runtime/object.cpp b/src/runtime/object.cpp
index c88b83876c..1b0322ed3d 100644
--- a/src/runtime/object.cpp
+++ b/src/runtime/object.cpp
@@ -1232,6 +1232,13 @@ static object * mpz_to_int(mpz const & m) {
         return lean_box(static_cast<unsigned>(m.get_int()));
 }
 
+extern "C" lean_obj_res lean_big_int_to_nat(lean_obj_arg a) {
+    lean_assert(!lean_is_scalar(a));
+    mpz m = mpz_value(a);
+    lean_dec(a);
+    return mpz_to_nat(m);
+}
+
 extern "C" object * lean_cstr_to_int(char const * n) {
     return mpz_to_int(mpz(n));
 }
diff --git a/tests/lean/run/int_to_nat_bug.lean b/tests/lean/run/int_to_nat_bug.lean
new file mode 100644
index 0000000000..b0068696fb
--- /dev/null
+++ b/tests/lean/run/int_to_nat_bug.lean
@@ -0,0 +1 @@
+#eval (4294967295 : Int)