diff --git a/tests/ef_tests/Cargo.toml b/tests/ef_tests/Cargo.toml
index 5535f1956..c4e1e9041 100644
--- a/tests/ef_tests/Cargo.toml
+++ b/tests/ef_tests/Cargo.toml
@@ -12,4 +12,4 @@ serde_derive = "1.0"
 serde_yaml = "0.8"
 ssz = { path = "../../eth2/utils/ssz" }
 types = { path = "../../eth2/types" }
-yaml-rust = "0.4"
+yaml-rust = { git = "https://github.com/sigp/yaml-rust", branch = "escape_all_str"}
diff --git a/tests/ef_tests/src/yaml_utils.rs b/tests/ef_tests/src/yaml_utils.rs
index 2e379a277..ae13ba3b4 100644
--- a/tests/ef_tests/src/yaml_utils.rs
+++ b/tests/ef_tests/src/yaml_utils.rs
@@ -17,6 +17,7 @@ pub fn extract_yaml_by_index(yaml: &str, index: usize) -> String {
 pub fn yaml_to_string(yaml: &Yaml) -> String {
     let mut out_str = String::new();
     let mut emitter = YamlEmitter::new(&mut out_str);
+    emitter.escape_all_strings(true);
     emitter.dump(yaml).unwrap();
 
     out_str