diff --git a/vlib/clipboard/x11/clipboard.c.v b/vlib/clipboard/x11/clipboard.c.v
index d4ffa2d9cc..ecd9f31db8 100644
--- a/vlib/clipboard/x11/clipboard.c.v
+++ b/vlib/clipboard/x11/clipboard.c.v
@@ -145,7 +145,7 @@ mut:
 	selection Atom // the selection atom
 	window    Window
 	atoms     []Atom
-	mutex     &sync.Mutex = unsafe { nil }
+	mutex     &sync.Mutex = sync.new_mutex()
 	text      string // text data sent or received
 	got_text  bool   // used to confirm that we have got the text
 	is_owner  bool   // to save selection owner state
diff --git a/vlib/context/cancel.v b/vlib/context/cancel.v
index c05b70b8cc..6851a18874 100644
--- a/vlib/context/cancel.v
+++ b/vlib/context/cancel.v
@@ -23,10 +23,10 @@ pub struct CancelContext {
 	id string
 mut:
 	context  Context
-	mutex    &sync.Mutex
+	mutex    &sync.Mutex = sync.new_mutex()
 	done     chan int
 	children map[string]Canceler
-	err      IError
+	err      IError = none
 }
 
 // with_cancel returns a copy of parent with a new done channel. The returned
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 4f60275807..f14cda6666 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -385,8 +385,8 @@ pub fn (mut p Parser) parse() &ast.File {
 struct Queue {
 mut:
 	idx              int
-	mu               &sync.Mutex
-	mu2              &sync.Mutex
+	mu               &sync.Mutex = sync.new_mutex()
+	mu2              &sync.Mutex = sync.new_mutex()
 	paths            []string
 	table            &ast.Table = unsafe { nil }
 	parsed_ast_files []&ast.File
diff --git a/vlib/v/tests/str_gen_test.v b/vlib/v/tests/str_gen_test.v
index 048049c569..9730d1f1c3 100644
--- a/vlib/v/tests/str_gen_test.v
+++ b/vlib/v/tests/str_gen_test.v
@@ -448,7 +448,7 @@ fn test_fixed_array_of_function() {
 }
 
 struct CTypeDefStruct {
-	mutex &sync.Mutex
+	mutex &sync.Mutex = sync.new_mutex()
 }
 
 fn test_c_struct_typedef() {