diff --git a/src/request_tab_widget.py b/src/request_tab_widget.py
index 96ef04d..be67f00 100644
--- a/src/request_tab_widget.py
+++ b/src/request_tab_widget.py
@@ -723,19 +723,28 @@ class RequestTabWidget(Gtk.Box):
 
     def _detect_undefined_variables(self):
         """Detect undefined variables in the current request. Returns set of undefined variable names."""
-        # Only detect if environment is selected
-        env = self.get_selected_environment()
-        if not env:
-            return set()
+        from .variable_substitution import VariableSubstitution
 
         # Get current request from UI
         request = self.get_request()
 
-        # Use VariableSubstitution to detect undefined variables
-        from .variable_substitution import VariableSubstitution
-        _, undefined = VariableSubstitution.substitute_request(request, env)
+        # Get selected environment
+        env = self.get_selected_environment()
 
-        return undefined
+        if not env:
+            # No environment selected - ALL variables are undefined
+            # Find all variables in the request
+            all_vars = set()
+            all_vars.update(VariableSubstitution.find_variables(request.url))
+            all_vars.update(VariableSubstitution.find_variables(request.body))
+            for key, value in request.headers.items():
+                all_vars.update(VariableSubstitution.find_variables(key))
+                all_vars.update(VariableSubstitution.find_variables(value))
+            return all_vars
+        else:
+            # Environment selected - find which variables are undefined
+            _, undefined = VariableSubstitution.substitute_request(request, env)
+            return undefined
 
     def _schedule_indicator_update(self):
         """Schedule an indicator update with debouncing."""