diff --git a/cpp/src/semal.cpp b/cpp/src/semal.cpp
index e2cd877..d297c90 100644
--- a/cpp/src/semal.cpp
+++ b/cpp/src/semal.cpp
@@ -548,6 +548,7 @@ namespace semal
 			d.assert_that(std::holds_alternative<ast::identifier>(payload.rhs_expr->expr), std::format("in a cast, rhs of the cast token \"{}\" must be an identifier, not an expression or anything else.", payload.op.lexeme));
 			std::string type_name = std::get<ast::identifier>(payload.rhs_expr->expr).iden;
 			rhs = d.state.get_type_from_name(type_name);
+			d.assert_that(lhs.is_explicitly_convertible_to(rhs), std::format("cast from \"{}\" to \"{}\" is impossible", lhs.name(), rhs.name()));
 			d.assert_that(!rhs.is_undefined(), std::format("unknown cast destination type \"{}\"", type_name));
 			// todo: confirm that lhs can actually be casted to rhs.
 		}
diff --git a/cpp/src/type.cpp b/cpp/src/type.cpp
index 7e41d05..8b1c09d 100644
--- a/cpp/src/type.cpp
+++ b/cpp/src/type.cpp
@@ -172,6 +172,12 @@ bool type::is_implicitly_convertible_to(const type& rhs) const
 	if(this->is_weak() || rhs.is_weak())
 	{
 		// weak types are implicitly convertible to a bunch of things.
+		auto plain_this = this->without_qualifiers();
+		if(plain_this == type::from_primitive(primitive_type::i64) && rhs.is_pointer())
+		{
+			// i64 -> any pointer (i.e uintptr_t)
+			return true;
+		}
 		if(this->is_integer_type() && rhs.is_integer_type())
 		{
 			// integer promotion.
diff --git a/samples/scratchpad.psy b/samples/scratchpad.psy
index 381a635..dc3176b 100644
--- a/samples/scratchpad.psy
+++ b/samples/scratchpad.psy
@@ -29,7 +29,7 @@ putchar :: (ch : i8) -> u0 := extern;
 dub :: (val : i64) -> i64
 {
 	vvptr : i64&& const;
-	deref vvptr = (55@i64&);
+	deref vvptr = (55@u64& weak);
 	vv : f64 weak := 5;
 	vv = 50;