diff --git a/lib/std/hash/fnv32a.c3 b/lib/std/hash/fnv32a.c3
index a0eddaeca..ad185d811 100644
--- a/lib/std/hash/fnv32a.c3
+++ b/lib/std/hash/fnv32a.c3
@@ -5,8 +5,8 @@ module std::hash::fnv32a;
 
 typedef Fnv32a = uint;
 
-const FNV32A_START @private = 0x811c9dc5;
-const FNV32A_MUL @private = 0x01000193;
+const FNV32A_START @private = (Fnv32a)0x811c9dc5;
+const FNV32A_MUL @private = (Fnv32a)0x01000193;
 
 macro void update(h, char x) @private => *h = (*h ^ ($typeof(*h))x) * FNV32A_MUL;
 
@@ -32,10 +32,10 @@ macro void Fnv32a.update_char(&self, char c)
 
 fn uint hash(char[] data)
 {
-	uint h = FNV32A_START;
+	Fnv32a h = FNV32A_START;
 	foreach (char x : data)
 	{
 		update(&h, x);
 	}
-	return h;
+	return (uint)h;
 }
diff --git a/lib/std/hash/fnv64a.c3 b/lib/std/hash/fnv64a.c3
index cd108710a..6500f90c4 100644
--- a/lib/std/hash/fnv64a.c3
+++ b/lib/std/hash/fnv64a.c3
@@ -5,10 +5,10 @@ module std::hash::fnv64a;
 
 typedef Fnv64a = ulong;
 
-const FNV64A_START @private = 0xcbf29ce484222325;
-const FNV64A_MUL @private = 0x00000100000001b3;
+const Fnv64a FNV64A_START @private = (Fnv64a)0xcbf29ce484222325;
+const Fnv64a FNV64A_MUL @private = (Fnv64a)0x00000100000001b3;
 
-macro void update(h, char x) @private => *h = (*h ^ ($typeof(*h))x) * FNV64A_MUL;
+macro Fnv64a update(Fnv64a h, char x) @nodiscard @private => (h ^ (Fnv64a)x) * FNV64A_MUL;
 
 fn void Fnv64a.init(&self)
 {
@@ -20,22 +20,22 @@ fn void Fnv64a.update(&self, char[] data)
 	Fnv64a h = *self;
 	foreach (char x : data)
 	{
-		update(&h, x);
+		h = update(h, x);
 	}
 	*self = h;
 }
 
 macro void Fnv64a.update_char(&self, char c)
 {
-	update(self, c);
+	*self = update(*self, c);
 }
 
 fn ulong hash(char[] data)
 {
-	ulong h = FNV64A_START;
+	Fnv64a h = FNV64A_START;
 	foreach (char x : data)
 	{
-		update(&h, x);
+		h = update(h, x);
 	}
-	return h;
+	return (ulong)h;
 }
diff --git a/lib/std/os/win32/shell32.c3 b/lib/std/os/win32/shell32.c3
index 504c3e586..9a2a40d66 100644
--- a/lib/std/os/win32/shell32.c3
+++ b/lib/std/os/win32/shell32.c3
@@ -1,6 +1,6 @@
 module std::os::win32 @if(env::WIN32) @link("shell32");
 
-typedef Win32_REFKNOWNFOLDERID = Win32_KNOWNFOLDERID*;
+alias Win32_REFKNOWNFOLDERID = Win32_KNOWNFOLDERID*;
 typedef Win32_KNOWNFOLDERID = Win32_GUID;
 extern fn Win32_HRESULT shGetKnownFolderPath(Win32_REFKNOWNFOLDERID rfid, Win32_DWORD dwFlags, Win32_HANDLE hToken, Win32_PWSTR* ppszPath) @cname("SHGetKnownFolderPath");
 
diff --git a/lib/std/threads/os/thread_none.c3 b/lib/std/threads/os/thread_none.c3
index b46457b06..65b1d731d 100644
--- a/lib/std/threads/os/thread_none.c3
+++ b/lib/std/threads/os/thread_none.c3
@@ -8,9 +8,9 @@ typedef NativeThread = int;
 
 fn void NativeOnceFlag.call_once(&flag, OnceFn func)
 {
-	if (*flag == 0)
+	if (*flag == (NativeOnceFlag)0)
 	{
-		*flag = 1;
+		*flag = (NativeOnceFlag)1;
 		func();
 	}
 }
diff --git a/releasenotes.md b/releasenotes.md
index 6de1552e9..06b4d134f 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -12,6 +12,8 @@
 - New const enum declaration syntax.
 - New enum associated value syntax.
 - Individual warning settings added.
+- Change typedef and const enums to not convert from literals by default.
+- Add `@constinit` to allow old typedef behaviour.
 
 ### Stdlib changes
 - Summarize sort macros as generic function wrappers to reduce the amount of generated code. #2831
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 81e530339..0c7a6cef1 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -717,6 +717,7 @@ typedef struct Decl_
 	bool resolved_attributes : 1;
 	bool allow_deprecated : 1;
 	bool attr_structlike : 1;
+	bool attr_constinit : 1;
 	bool is_template : 1;
 	bool is_templated : 1;
 	bool is_method_checked : 1;
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index 4ba0ff942..e35c9a0f8 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -628,6 +628,7 @@ typedef enum
 	ATTRIBUTE_CNAME,
 	ATTRIBUTE_COMPACT,
 	ATTRIBUTE_CONST,
+	ATTRIBUTE_CONSTINIT,
 	ATTRIBUTE_DEPRECATED,
 	ATTRIBUTE_DYNAMIC,
 	ATTRIBUTE_EXPORT,
diff --git a/src/compiler/sema_casts.c b/src/compiler/sema_casts.c
index 878b84686..2ea4ea2ad 100644
--- a/src/compiler/sema_casts.c
+++ b/src/compiler/sema_casts.c
@@ -1459,15 +1459,24 @@ static bool rule_to_distinct(CastContext *cc, bool is_explicit, bool is_silent)
 	{
 		is_const = true;
 	}
-	if (is_const && (cc->is_binary_conversion || !cc->to->decl->attr_structlike))
+	if (is_const && (cc->is_binary_conversion || cc->to->decl->attr_constinit || !cc->to->decl->attr_structlike))
 	{
+		Type *to_type = cc->to;
 		cc->to = flat;
 		cc->to_group = flat_group;
 
 		// If it's silent or explicit, just run it:
 		if (is_silent || is_explicit) return cast_is_allowed(cc, is_explicit, is_silent);
 		// Loud and implicit:
-		if (cast_is_allowed(cc, false, true)) return true;
+		if (cast_is_allowed(cc, false, true))
+		{
+			if (!cc->is_binary_conversion && !to_type->decl->attr_constinit && !expr_is_const_untyped_list(cc->expr))
+			{
+				to_type->decl->attr_constinit = true;
+				SEMA_DEPRECATED(cc->expr, "Implicit conversion of constants to distinct types is deprecated, use @constinit if %s should cast constants to its own type.", type_quoted_error_string(to_type));
+			}
+			return true;
+		}
 		return sema_cast_error(cc, cast_is_allowed(cc, true, true), is_silent);
 	}
 
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index a6bd06834..4560424f4 100644
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -3128,6 +3128,7 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 			[ATTRIBUTE_CNAME] = ATTR_FUNC | ATTR_GLOBAL | ATTR_CONST | USER_DEFINED_TYPES,
 			[ATTRIBUTE_COMPACT] = ATTR_STRUCT | ATTR_UNION,
 			[ATTRIBUTE_CONST] = ATTR_MACRO,
+			[ATTRIBUTE_CONSTINIT] = ATTR_TYPEDEF | ATTR_ENUM,
 			[ATTRIBUTE_DEPRECATED] = USER_DEFINED_TYPES | CALLABLE_TYPE | ATTR_CONST | ATTR_GLOBAL | ATTR_MEMBER | ATTR_BITSTRUCT_MEMBER | ATTR_INTERFACE | ATTR_ALIAS,
 			[ATTRIBUTE_DYNAMIC] = ATTR_FUNC,
 			[ATTRIBUTE_EXPORT] = ATTR_FUNC | ATTR_GLOBAL | ATTR_CONST | USER_DEFINED_TYPES | ATTR_ALIAS,
@@ -3471,6 +3472,9 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 		case ATTRIBUTE_STRUCTLIKE:
 			decl->attr_structlike = true;
 			return true;
+		case ATTRIBUTE_CONSTINIT:
+			decl->attr_constinit = true;
+			return true;
 		case ATTRIBUTE_SIMD:
 			RETURN_SEMA_ERROR(attr, "'@simd' is only allowed on typedef types.");
 		case ATTRIBUTE_SECTION:
diff --git a/src/compiler/symtab.c b/src/compiler/symtab.c
index bcc4bd296..ec5bbc754 100644
--- a/src/compiler/symtab.c
+++ b/src/compiler/symtab.c
@@ -347,6 +347,7 @@ void symtab_init(uint32_t capacity)
 	attribute_list[ATTRIBUTE_CNAME] = KW_DEF("@cname");
 	attribute_list[ATTRIBUTE_COMPACT] = KW_DEF("@compact");
 	attribute_list[ATTRIBUTE_CONST] = KW_DEF("@const");
+	attribute_list[ATTRIBUTE_CONSTINIT] = KW_DEF("@constinit");
 	attribute_list[ATTRIBUTE_DEPRECATED] = KW_DEF("@deprecated");
 	attribute_list[ATTRIBUTE_DYNAMIC] = KW_DEF("@dynamic");
 	attribute_list[ATTRIBUTE_EXPORT] = KW_DEF("@export");
diff --git a/test/test_suite/distinct/test_ops_on_int.c3 b/test/test_suite/distinct/test_ops_on_int.c3
index 853195695..331c1b854 100644
--- a/test/test_suite/distinct/test_ops_on_int.c3
+++ b/test/test_suite/distinct/test_ops_on_int.c3
@@ -1,6 +1,6 @@
 module test;
 
-typedef Foo = int;
+typedef Foo @constinit = int;
 
 fn int test1()
 {
diff --git a/test/test_suite/enumerations/enum_const.c3t b/test/test_suite/enumerations/enum_const.c3t
index 304867db2..147ffc728 100644
--- a/test/test_suite/enumerations/enum_const.c3t
+++ b/test/test_suite/enumerations/enum_const.c3t
@@ -24,7 +24,7 @@ const enum Bde2 :  int
 	BAR = 100
 }
 
-typedef Bde3 = int;
+typedef Bde3 @constinit = int;
 const BDE3_FOO = 2;
 const BDE3_BAR = 100;