diff --git a/src/manifest/mod.rs b/src/manifest/mod.rs
index 790a6c9..54f7740 100644
--- a/src/manifest/mod.rs
+++ b/src/manifest/mod.rs
@@ -723,10 +723,10 @@ impl CrateData {
                 url: repo_url,
             }),
             files: data.files,
-            module: data.main,
+            module: data.main.clone(),
             homepage: data.homepage,
             types: data.dts_file,
-            side_effects: false,
+            side_effects: vec![format!("./{}", data.main), "./snippets/*".to_owned()],
             keywords: data.keywords,
             dependencies,
         })
@@ -758,7 +758,7 @@ impl CrateData {
             module: data.main,
             homepage: data.homepage,
             types: data.dts_file,
-            side_effects: false,
+            side_effects: vec!["./snippets/*".to_owned()],
             keywords: data.keywords,
             dependencies,
         })
diff --git a/src/manifest/npm/esmodules.rs b/src/manifest/npm/esmodules.rs
index 2501a6c..7d216bc 100644
--- a/src/manifest/npm/esmodules.rs
+++ b/src/manifest/npm/esmodules.rs
@@ -22,7 +22,7 @@ pub struct ESModulesPackage {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub types: Option<String>,
     #[serde(rename = "sideEffects")]
-    pub side_effects: bool,
+    pub side_effects: Vec<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub keywords: Option<Vec<String>>,
     #[serde(skip_serializing_if = "Option::is_none")]
diff --git a/tests/all/manifest.rs b/tests/all/manifest.rs
index 48d17df..abf0e75 100644
--- a/tests/all/manifest.rs
+++ b/tests/all/manifest.rs
@@ -93,7 +93,10 @@ fn it_creates_a_package_json_default_path() {
     );
     assert_eq!(pkg.module, "js_hello_world.js");
     assert_eq!(pkg.types, "js_hello_world.d.ts");
-    assert_eq!(pkg.side_effects, false);
+    assert_eq!(
+        pkg.side_effects,
+        vec!["./js_hello_world.js", "./snippets/*"]
+    );
 
     let actual_files: HashSet<String> = pkg.files.into_iter().collect();
     let expected_files: HashSet<String> = [
@@ -255,7 +258,7 @@ fn it_creates_a_package_json_with_correct_files_when_out_name_is_provided() {
     );
     assert_eq!(pkg.module, "index.js");
     assert_eq!(pkg.types, "index.d.ts");
-    assert_eq!(pkg.side_effects, false);
+    assert_eq!(pkg.side_effects, vec!["./index.js", "./snippets/*"]);
 
     let actual_files: HashSet<String> = pkg.files.into_iter().collect();
     let expected_files: HashSet<String> =
diff --git a/tests/all/utils/manifest.rs b/tests/all/utils/manifest.rs
index 3a788de..9e34d72 100644
--- a/tests/all/utils/manifest.rs
+++ b/tests/all/utils/manifest.rs
@@ -21,8 +21,8 @@ pub struct NpmPackage {
     pub browser: String,
     #[serde(default = "default_none")]
     pub types: String,
-    #[serde(default = "default_false", rename = "sideEffects")]
-    pub side_effects: bool,
+    #[serde(default = "Vec::new", rename = "sideEffects")]
+    pub side_effects: Vec<String>,
     pub homepage: Option<String>,
     pub keywords: Option<Vec<String>>,
     pub dependencies: Option<HashMap<String, String>>,
@@ -32,10 +32,6 @@ fn default_none() -> String {
     "".to_string()
 }
 
-fn default_false() -> bool {
-    false
-}
-
 #[derive(Deserialize)]
 pub struct Repository {
     #[serde(rename = "type")]