diff --git a/erpnext/projects/doctype/time_log/time_log.py b/erpnext/projects/doctype/time_log/time_log.py
index 7bb083501e..a829d4449f 100644
--- a/erpnext/projects/doctype/time_log/time_log.py
+++ b/erpnext/projects/doctype/time_log/time_log.py
@@ -24,6 +24,7 @@ class TimeLog(Document):
 		self.check_workstation_timings()
 		self.validate_production_order()
 		self.validate_project()
+		self.validate_activity()
 
 	def on_submit(self):
 		self.update_production_order()
@@ -134,6 +135,11 @@ class TimeLog(Document):
 			if not self.project:
 				frappe.throw(_("Project is Mandatory."))
 
+	def validate_activity(self):
+		if self.time_log_for == 'Project':
+			if not self.activity:
+				frappe.throw(_("Activity is Mandatory."))
+
 @frappe.whitelist()
 def get_workstation(production_order, operation):
 	"""Returns workstation name from Production Order against an associated Operation.