diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 3b5b54abb7..44d3500d39 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -7332,7 +7332,7 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 			// the deferred statements are generated.
 			g.write_defer_stmts()
 			// Now that option types are distinct we need a cast here
-			if g.fn_decl.return_type == ast.void_type {
+			if g.fn_decl == unsafe { nil } || g.fn_decl.return_type == ast.void_type {
 				g.writeln('\treturn;')
 			} else {
 				styp := g.styp(g.fn_decl.return_type)
@@ -7360,7 +7360,7 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 			// the deferred statements are generated.
 			g.write_defer_stmts()
 			// Now that option types are distinct we need a cast here
-			if g.fn_decl.return_type == ast.void_type {
+			if g.fn_decl == unsafe { nil } || g.fn_decl.return_type == ast.void_type {
 				g.writeln('\treturn;')
 			} else {
 				styp := g.styp(g.fn_decl.return_type).replace('*', '_ptr')
diff --git a/vlib/v/tests/options/modules/mymod/mod.v b/vlib/v/tests/options/modules/mymod/mod.v
new file mode 100644
index 0000000000..2b845ae565
--- /dev/null
+++ b/vlib/v/tests/options/modules/mymod/mod.v
@@ -0,0 +1,16 @@
+// mod.v
+
+module mymod
+
+import math.big
+
+pub struct BigintRange {
+pub mut:
+	start big.Integer
+	end   big.Integer
+}
+
+pub const range = BigintRange{
+	start: big.integer_from_string('338288524927261089654018896841347694592')!
+	end:   big.integer_from_string('338620831926207318622244848606417780735')!
+}
diff --git a/vlib/v/tests/options/modules/mymod/mod_test.v b/vlib/v/tests/options/modules/mymod/mod_test.v
new file mode 100644
index 0000000000..526f94deb3
--- /dev/null
+++ b/vlib/v/tests/options/modules/mymod/mod_test.v
@@ -0,0 +1,7 @@
+// mod_test.v
+
+module mymod
+
+fn test_dummy() {
+	assert range != BigintRange{}
+}