diff --git a/crates/cli/src/commands/server.rs b/crates/cli/src/commands/server.rs
index 1367f131e..52465f077 100644
--- a/crates/cli/src/commands/server.rs
+++ b/crates/cli/src/commands/server.rs
@@ -160,8 +160,14 @@ impl Options {
         )?;
 
         // Load and compile the templates
-        let templates =
-            templates_from_config(&config.templates, &site_config, &url_builder).await?;
+        let templates = templates_from_config(
+            &config.templates,
+            &site_config,
+            &url_builder,
+            // Don't use strict mode in production yet
+            false,
+        )
+        .await?;
         shutdown.register_reloadable(&templates);
 
         let http_client = mas_http::reqwest_client();
diff --git a/crates/cli/src/commands/templates.rs b/crates/cli/src/commands/templates.rs
index 111f19682..6665f7f23 100644
--- a/crates/cli/src/commands/templates.rs
+++ b/crates/cli/src/commands/templates.rs
@@ -65,8 +65,14 @@ impl Options {
                     &account_config,
                     &captcha_config,
                 )?;
-                let templates =
-                    templates_from_config(&template_config, &site_config, &url_builder).await?;
+                let templates = templates_from_config(
+                    &template_config,
+                    &site_config,
+                    &url_builder,
+                    // Use strict mode in template checks
+                    true,
+                )
+                .await?;
                 templates.check_render(clock.now(), &mut rng)?;
 
                 Ok(ExitCode::SUCCESS)
diff --git a/crates/cli/src/commands/worker.rs b/crates/cli/src/commands/worker.rs
index 31d0d56c2..a1eb0fcce 100644
--- a/crates/cli/src/commands/worker.rs
+++ b/crates/cli/src/commands/worker.rs
@@ -52,8 +52,14 @@ impl Options {
         )?;
 
         // Load and compile the templates
-        let templates =
-            templates_from_config(&config.templates, &site_config, &url_builder).await?;
+        let templates = templates_from_config(
+            &config.templates,
+            &site_config,
+            &url_builder,
+            // Don't use strict mode on task workers for now
+            false,
+        )
+        .await?;
 
         let mailer = mailer_from_config(&config.email, &templates)?;
         test_mailer_in_background(&mailer, Duration::from_secs(30));
diff --git a/crates/cli/src/util.rs b/crates/cli/src/util.rs
index 976a08c32..4925d9866 100644
--- a/crates/cli/src/util.rs
+++ b/crates/cli/src/util.rs
@@ -232,6 +232,7 @@ pub async fn templates_from_config(
     config: &TemplatesConfig,
     site_config: &SiteConfig,
     url_builder: &UrlBuilder,
+    strict: bool,
 ) -> Result<Templates, anyhow::Error> {
     Templates::load(
         config.path.clone(),
@@ -240,6 +241,7 @@ pub async fn templates_from_config(
         config.translations_path.clone(),
         site_config.templates_branding(),
         site_config.templates_features(),
+        strict,
     )
     .await
     .with_context(|| format!("Failed to load the templates at {}", config.path))
diff --git a/crates/handlers/src/test_utils.rs b/crates/handlers/src/test_utils.rs
index fa8105763..f1859f352 100644
--- a/crates/handlers/src/test_utils.rs
+++ b/crates/handlers/src/test_utils.rs
@@ -176,6 +176,8 @@ impl TestState {
             workspace_root.join("translations"),
             site_config.templates_branding(),
             site_config.templates_features(),
+            // Strict mode in testing
+            true,
         )
         .await?;
 
diff --git a/crates/templates/src/lib.rs b/crates/templates/src/lib.rs
index daa34c0c5..ee8a6282e 100644
--- a/crates/templates/src/lib.rs
+++ b/crates/templates/src/lib.rs
@@ -71,6 +71,9 @@ pub struct Templates {
     vite_manifest_path: Utf8PathBuf,
     translations_path: Utf8PathBuf,
     path: Utf8PathBuf,
+    /// Whether template rendering is in strict mode (for testing,
+    /// until this can be rolled out in production.)
+    strict: bool,
 }
 
 /// There was an issue while loading the templates
@@ -151,6 +154,7 @@ impl Templates {
         translations_path: Utf8PathBuf,
         branding: SiteBranding,
         features: SiteFeatures,
+        strict: bool,
     ) -> Result<Self, TemplateLoadingError> {
         let (translator, environment) = Self::load_(
             &path,
@@ -159,6 +163,7 @@ impl Templates {
             &translations_path,
             branding.clone(),
             features,
+            strict,
         )
         .await?;
         Ok(Self {
@@ -170,6 +175,7 @@ impl Templates {
             translations_path,
             branding,
             features,
+            strict,
         })
     }
 
@@ -180,6 +186,7 @@ impl Templates {
         translations_path: &Utf8Path,
         branding: SiteBranding,
         features: SiteFeatures,
+        strict: bool,
     ) -> Result<(Arc<Translator>, Arc<minijinja::Environment<'static>>), TemplateLoadingError> {
         let path = path.to_owned();
         let span = tracing::Span::current();
@@ -206,7 +213,14 @@ impl Templates {
                 let mut loaded: HashSet<_> = HashSet::new();
                 let mut env = minijinja::Environment::new();
                 // Don't allow use of undefined variables
-                env.set_undefined_behavior(UndefinedBehavior::Strict);
+                env.set_undefined_behavior(if strict {
+                    UndefinedBehavior::Strict
+                } else {
+                    // For now, allow semi-strict, because we don't have total test coverage of
+                    // tests and some tests rely on if conditions against sometimes-undefined
+                    // variables
+                    UndefinedBehavior::SemiStrict
+                });
                 let root = path.canonicalize_utf8()?;
                 info!(%root, "Loading templates from filesystem");
                 for entry in walkdir::WalkDir::new(&root)
@@ -277,6 +291,7 @@ impl Templates {
             &self.translations_path,
             self.branding.clone(),
             self.features,
+            self.strict,
         )
         .await?;
 
@@ -526,6 +541,8 @@ mod tests {
             translations_path,
             branding,
             features,
+            // Use strict mode in tests
+            true,
         )
         .await
         .unwrap();