diff --git a/bitbake/lib/bb/build.py b/bitbake/lib/bb/build.py
index ab8bce3d57..d226aadacb 100644
--- a/bitbake/lib/bb/build.py
+++ b/bitbake/lib/bb/build.py
@@ -932,9 +932,13 @@ def add_tasks(tasklist, d):
     # don't assume holding a reference
     d.setVar('_task_deps', task_deps)
 
+def ensure_task_prefix(name):
+    if name[:3] != "do_":
+        name = "do_" + name
+    return name
+
 def addtask(task, before, after, d):
-    if task[:3] != "do_":
-        task = "do_" + task
+    task = ensure_task_prefix(task)
 
     d.setVarFlag(task, "task", 1)
     bbtasks = d.getVar('__BBTASKS', False) or []
@@ -946,19 +950,20 @@ def addtask(task, before, after, d):
     if after is not None:
         # set up deps for function
         for entry in after.split():
+            entry = ensure_task_prefix(entry)
             if entry not in existing:
                 existing.append(entry)
     d.setVarFlag(task, "deps", existing)
     if before is not None:
         # set up things that depend on this func
         for entry in before.split():
+            entry = ensure_task_prefix(entry)
             existing = d.getVarFlag(entry, "deps", False) or []
             if task not in existing:
                 d.setVarFlag(entry, "deps", [task] + existing)
 
 def deltask(task, d):
-    if task[:3] != "do_":
-        task = "do_" + task
+    task = ensure_task_prefix(task)
 
     bbtasks = d.getVar('__BBTASKS', False) or []
     if task in bbtasks:
diff --git a/bitbake/lib/bb/tests/parse.py b/bitbake/lib/bb/tests/parse.py
index 97df2c4590..410679d5a1 100644
--- a/bitbake/lib/bb/tests/parse.py
+++ b/bitbake/lib/bb/tests/parse.py
@@ -188,6 +188,9 @@ addtask do_mytask3
 deltask do_mytask3# comment
 deltask do_mytask4 # comment2
 
+# Ensure a missing task prefix on after works
+addtask do_mytask5 after mytask
+
 MYVAR = "do_patch"
 EMPTYVAR = ""
 deltask do_fetch ${MYVAR} ${EMPTYVAR}
@@ -198,7 +201,8 @@ deltask ${EMPTYVAR}
         f = self.parsehelper(self.addtask_deltask)
         d = bb.parse.handle(f.name, self.d)['']
 
-        self.assertEqual(['do_fetch2', 'do_patch2', 'do_myplaintask', 'do_mytask', 'do_mytask2'], d.getVar("__BBTASKS"))
+        self.assertEqual(['do_fetch2', 'do_patch2', 'do_myplaintask', 'do_mytask', 'do_mytask2', 'do_mytask5'], d.getVar("__BBTASKS"))
+        self.assertEqual(['do_mytask'], d.getVarFlag("do_mytask5", "deps"))
 
     broken_multiline_comment = """
 # First line of comment \\