diff --git a/src/core/inttypes.c b/src/core/inttypes.c
index c576e89d..f6f07c13 100644
--- a/src/core/inttypes.c
+++ b/src/core/inttypes.c
@@ -440,6 +440,14 @@ static Janet cfun_it_##type##_##name##i(int32_t argc, Janet *argv) { \
     return janet_wrap_abstract(box); \
 } \
 
+#define UNARYMETHOD(T, type, name, oper) \
+static Janet cfun_it_##type##_##name(int32_t argc, Janet *argv) { \
+    janet_fixarity(argc, 1); \
+    T *box = janet_abstract(&janet_##type##_type, sizeof(T)); \
+    *box = oper(janet_unwrap_##type(argv[0])); \
+    return janet_wrap_abstract(box); \
+} \
+
 #define DIVZERO(name) DIVZERO_##name
 #define DIVZERO_div janet_panic("division by zero")
 #define DIVZERO_rem janet_panic("division by zero")
@@ -556,6 +564,7 @@ DIVMETHODINVERT_SIGNED(int64_t, s64, rem, %)
 OPMETHOD(int64_t, s64, and, &)
 OPMETHOD(int64_t, s64, or, |)
 OPMETHOD(int64_t, s64, xor, ^)
+UNARYMETHOD(int64_t, s64, not, ~)
 OPMETHOD(int64_t, s64, lshift, <<)
 OPMETHOD(int64_t, s64, rshift, >>)
 OPMETHOD(uint64_t, u64, add, +)
@@ -571,6 +580,7 @@ DIVMETHODINVERT(uint64_t, u64, mod, %)
 OPMETHOD(uint64_t, u64, and, &)
 OPMETHOD(uint64_t, u64, or, |)
 OPMETHOD(uint64_t, u64, xor, ^)
+UNARYMETHOD(int64_t, u64, not, ~)
 OPMETHOD(uint64_t, u64, lshift, <<)
 OPMETHOD(uint64_t, u64, rshift, >>)
 
@@ -600,6 +610,7 @@ static JanetMethod it_s64_methods[] = {
     {"r|", cfun_it_s64_or},
     {"^", cfun_it_s64_xor},
     {"r^", cfun_it_s64_xor},
+    {"~", cfun_it_s64_not},
     {"<<", cfun_it_s64_lshift},
     {">>", cfun_it_s64_rshift},
     {"compare", cfun_it_s64_compare},
@@ -627,6 +638,7 @@ static JanetMethod it_u64_methods[] = {
     {"r|", cfun_it_u64_or},
     {"^", cfun_it_u64_xor},
     {"r^", cfun_it_u64_xor},
+    {"~", cfun_it_u64_not},
     {"<<", cfun_it_u64_lshift},
     {">>", cfun_it_u64_rshift},
     {"compare", cfun_it_u64_compare},
diff --git a/src/core/vm.c b/src/core/vm.c
index cdc932ce..00b9de04 100644
--- a/src/core/vm.c
+++ b/src/core/vm.c
@@ -301,6 +301,16 @@ static Janet janet_method_lookup(Janet x, const char *name) {
     return method_to_fun(janet_ckeywordv(name), x);
 }
 
+static Janet janet_unary_call(const char *method, Janet arg) {
+    Janet m = janet_method_lookup(arg, method);
+    if (janet_checktype(m, JANET_NIL)) {
+        janet_panicf("could not find method :%s for %v", method, arg);
+    } else {
+        Janet argv[1] = { arg };
+        return janet_method_invoke(m, 1, argv);
+    }
+}
+
 /* Call a method first on the righthand side, and then on the left hand side with a prefix */
 static Janet janet_binop_call(const char *lmethod, const char *rmethod, Janet lhs, Janet rhs) {
     Janet lm = janet_method_lookup(lhs, lmethod);
@@ -749,9 +759,14 @@ static JanetSignal run_vm(JanetFiber *fiber, Janet in) {
 
     VM_OP(JOP_BNOT) {
         Janet op = stack[E];
-        vm_assert_type(op, JANET_NUMBER);
-        stack[A] = janet_wrap_integer(~janet_unwrap_integer(op));
-        vm_pcnext();
+        if (janet_checktype(op, JANET_NUMBER)) {
+            stack[A] = janet_wrap_integer(~janet_unwrap_integer(op));
+            vm_pcnext();
+        } else {
+            vm_commit();
+            stack[A] = janet_unary_call("~", op);
+            vm_checkgc_pcnext();
+        }
     }
 
     VM_OP(JOP_SHIFT_RIGHT_UNSIGNED)