diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 5118dd0..340c982 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -6,6 +6,10 @@
 
 == [Unreleased]
 
+== Fixed
+
+- fix serializing strings containing `:`
+
 == [v0.2.4] - 2023-03-01
 
 == Fixed
diff --git a/src/ser.rs b/src/ser.rs
index 7b28706..1364ba2 100644
--- a/src/ser.rs
+++ b/src/ser.rs
@@ -123,7 +123,7 @@ impl<'a> serde::ser::Serializer for &'a mut Serializer {
         self.ensure_top_level_struct()?;
 
         let needs_quotes =
-            v.is_empty() || v.contains([' ', '\n', '\r', '\t', '=', '\'', '"', '\\', '/']);
+            v.is_empty() || v.contains([' ', '\n', '\r', '\t', '=', '\'', '"', '\\', ':']);
 
         if needs_quotes {
             self.output += "\"";