diff --git a/src/build/build_options.c b/src/build/build_options.c
index 09f798d35..482c62d22 100644
--- a/src/build/build_options.c
+++ b/src/build/build_options.c
@@ -387,7 +387,7 @@ static void print_all_targets(void)
 
 static void print_version(void)
 {
-	OUTPUT("C3 Compiler Version (pre-alpha):   %s", COMPILER_VERSION);
+	OUTPUT("C3 Compiler Version (alpha):       %s", COMPILER_VERSION);
 	OUTPUT("Installed directory:               %s", find_executable_path());
 	OUTPUT("LLVM version:                      %s", llvm_version);
 	OUTPUT("LLVM default target:               %s", llvm_target);
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index ff5ccaa83..84861f806 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -416,13 +416,11 @@ static bool sema_binary_is_expr_lvalue(Expr *top_expr, Expr *expr)
 			Decl *decl = expr->identifier_expr.decl;
 			if (decl->decl_kind != DECL_VAR)
 			{
-				SEMA_ERROR(top_expr, "You cannot assign a value to %s.", decl_to_a_name(decl));
-				return false;
+				RETURN_SEMA_ERROR(top_expr, "You cannot assign a value to %s.", decl_to_a_name(decl));
 			}
 			if (decl->var.kind == VARDECL_CONST)
 			{
-				SEMA_ERROR(top_expr, "You cannot assign to a constant.");
-				return false;
+				RETURN_SEMA_ERROR(top_expr, "You cannot assign to a constant.");
 			}
 			decl = decl_raw(decl);
 			switch (decl->var.kind)
@@ -469,16 +467,16 @@ static bool sema_binary_is_expr_lvalue(Expr *top_expr, Expr *expr)
 		case EXPR_SUBSCRIPT_ADDR:
 			if (IS_OPTIONAL(expr))
 			{
-				SEMA_ERROR(top_expr, "You cannot assign to an optional value.");
-				return false;
+				RETURN_SEMA_ERROR(top_expr, "You cannot assign to an optional value.");
 			}
 			return true;
 		case EXPR_HASH_IDENT:
-			SEMA_ERROR(top_expr, "You cannot assign to an unevaluated expression.");
-			return false;
+			RETURN_SEMA_ERROR(top_expr, "You cannot assign to an unevaluated expression.");
 		case EXPR_EXPRESSION_LIST:
 			if (!vec_size(expr->expression_list)) return false;
 			return sema_binary_is_expr_lvalue(top_expr, VECLAST(expr->expression_list));
+		case EXPR_CONST:
+			RETURN_SEMA_ERROR(top_expr, "You cannot assign to a constant expression.");
 		case EXPR_POISONED:
 		case EXPR_ASM:
 		case EXPR_BINARY:
@@ -491,7 +489,6 @@ static bool sema_binary_is_expr_lvalue(Expr *top_expr, Expr *expr)
 		case EXPR_COMPILER_CONST:
 		case EXPR_COMPOUND_LITERAL:
 		case EXPR_COND:
-		case EXPR_CONST:
 		case EXPR_CT_ARG:
 		case EXPR_CT_CALL:
 		case EXPR_CT_AND_OR:
diff --git a/src/version.h b/src/version.h
index fbaf6a781..0e47f0154 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.5.0"
+#define COMPILER_VERSION "0.5.1"
diff --git a/test/test_suite/constants/assign_to_const.c3 b/test/test_suite/constants/assign_to_const.c3
new file mode 100644
index 000000000..b6574ec07
--- /dev/null
+++ b/test/test_suite/constants/assign_to_const.c3
@@ -0,0 +1,8 @@
+module test;
+import std::io;
+
+fn void main()
+{
+	const NUM = 4;
+	NUM += 1; // #error: You cannot assign to a constant expression
+}
\ No newline at end of file
diff --git a/test/test_suite/expressions/arithmetics_sema_fail.c3 b/test/test_suite/expressions/arithmetics_sema_fail.c3
index ffb6dda03..5612ed71e 100644
--- a/test/test_suite/expressions/arithmetics_sema_fail.c3
+++ b/test/test_suite/expressions/arithmetics_sema_fail.c3
@@ -17,32 +17,32 @@ fn void test9()
 
 fn void test10()
 {
-    10 = 20;        // #error: An assignable expression
+    10 = 20;        // #error: to a constant expression
 }
 
 fn void test11()
 {
-    '10' = '20';        // #error: An assignable expression
+    '10' = '20';        // #error: to a constant expression
 }
 
 fn void test12()
 {
-    true = false;        // #error: An assignable expression
+    true = false;        // #error: to a constant expression
 }
 
 fn void test13()
 {
-    "a" = "b";        // #error: An assignable expression
+    "a" = "b";        // #error: to a constant expression
 }
 
 fn void test14()
 {
-    1.2 = 1.3;        // #error: An assignable expression
+    1.2 = 1.3;        // #error: to a constant expression
 }
 
 fn void test15()
 {
-    null = null;      // #error: An assignable expression
+    null = null;      // #error: to a constant expression
 }
 
 fn void test16()
diff --git a/test/test_suite/expressions/assignability.c3 b/test/test_suite/expressions/assignability.c3
index 8cbc5bde7..4f8825393 100644
--- a/test/test_suite/expressions/assignability.c3
+++ b/test/test_suite/expressions/assignability.c3
@@ -2,27 +2,27 @@ def Number = int;
 
 fn void test1()
 {
-    10 = 20;        // #error: An assignable expression
+    10 = 20;        // #error: to a constant expression
 }
 
 fn void test2()
 {
-    "foo" = "bar";  // #error: An assignable expression
+    "foo" = "bar";  // #error: to a constant expression
 }
 
 fn void test3()
 {
-    true = false;   // #error: An assignable expression
+    true = false;   // #error: to a constant expression
 }
 
 fn void test4()
 {
-    'c' = 'd';      // #error: An assignable expression
+    'c' = 'd';      // #error: to a constant expression
 }
 
 fn void test5()
 {
-    3.14 = 2.14;    // #error: An assignable expression
+    3.14 = 2.14;    // #error: to a constant expression
 }
 
 fn void test21()