diff --git a/artiq/compiler/builtins.py b/artiq/compiler/builtins.py
index 57d506b78..9ae3e22b1 100644
--- a/artiq/compiler/builtins.py
+++ b/artiq/compiler/builtins.py
@@ -150,6 +150,9 @@ def obj_parallel():
 def obj_sequential():
     return types.TBuiltin("sequential")
 
+def fn_watchdog():
+    return types.TBuiltinFunction("watchdog")
+
 def fn_now():
     return types.TBuiltinFunction("now")
 
diff --git a/artiq/compiler/prelude.py b/artiq/compiler/prelude.py
index 34ecd9695..4c616a3c4 100644
--- a/artiq/compiler/prelude.py
+++ b/artiq/compiler/prelude.py
@@ -31,6 +31,7 @@ def globals():
         # ARTIQ context managers
         "parallel":             builtins.obj_parallel(),
         "sequential":           builtins.obj_sequential(),
+        "watchdog":             builtins.fn_watchdog(),
 
         # ARTIQ time management functions
         "now":                  builtins.fn_now(),
diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py
index 5053444f3..55f6bfadb 100644
--- a/artiq/compiler/transforms/artiq_ir_generator.py
+++ b/artiq/compiler/transforms/artiq_ir_generator.py
@@ -714,6 +714,32 @@ class ARTIQIRGenerator(algorithm.Visitor):
             for tail in tails:
                 if not tail.is_terminated():
                     tail.append(ir.Branch(self.current_block))
+        elif isinstance(context_expr_node, asttyped.CallT) and \
+                types.is_builtin(context_expr_node.func.type, "watchdog"):
+            timeout        = self.visit(context_expr_node.args[0])
+            timeout_ms     = self.append(ir.Arith(ast.Mult(loc=None), timeout,
+                                                  ir.Constant(1000, builtins.TFloat())))
+            timeout_ms_int = self.append(ir.Coerce(timeout_ms, builtins.TInt32()))
+
+            watchdog   = self.append(ir.Builtin("watchdog_set", [timeout_ms_int], builtins.TInt32()))
+
+            dispatcher = self.add_block("watchdog.dispatch")
+
+            try:
+                old_unwind, self.unwind_target = self.unwind_target, dispatcher
+                self.visit(node.body)
+            finally:
+                self.unwind_target = old_unwind
+
+            cleanup = self.add_block('watchdog.cleanup')
+            landingpad = dispatcher.append(ir.LandingPad(cleanup))
+            cleanup.append(ir.Builtin("watchdog_clear", [watchdog], builtins.TNone()))
+            cleanup.append(ir.Reraise(self.unwind_target))
+
+            if not self.current_block.is_terminated():
+                self.append(ir.Builtin("watchdog_clear", [watchdog], builtins.TNone()))
+        else:
+            assert False
 
     # Expression visitors
     # These visitors return a node in addition to mutating
@@ -1551,7 +1577,11 @@ class ARTIQIRGenerator(algorithm.Visitor):
         elif types.is_constructor(typ):
             return self.append(ir.Alloc([], typ.instance))
         else:
-            assert False
+            diag = diagnostic.Diagnostic("error",
+                "builtin function '{name}' cannot be used in this context",
+                {"name": typ.name},
+                node.loc)
+            self.engine.process(diag)
 
     def visit_CallT(self, node):
         typ = node.func.type.find()
diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index 95d7f3fc6..b9bb7554e 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -757,6 +757,9 @@ class Inferencer(algorithm.Visitor):
         elif types.is_builtin(typ, "seconds_to_mu"):
             simple_form("seconds_to_mu(time:float) -> int(width=64)",
                         [builtins.TFloat()], builtins.TInt64())
+        elif types.is_builtin(typ, "watchdog"):
+            simple_form("watchdog(time:float) -> [builtin context manager]",
+                        [builtins.TFloat()], builtins.TNone())
         elif types.is_constructor(typ):
             # An user-defined class.
             self._unify(node.type, typ.find().instance,
@@ -942,7 +945,10 @@ class Inferencer(algorithm.Visitor):
         self.generic_visit(node)
 
         typ = node.context_expr.type
-        if not (types.is_builtin(typ, "parallel") or types.is_builtin(typ, "sequential")):
+        if not (types.is_builtin(typ, "parallel") or
+                types.is_builtin(typ, "sequential") or
+                (isinstance(node.context_expr, asttyped.CallT) and
+                 types.is_builtin(node.context_expr.func.type, "watchdog"))):
             diag = diagnostic.Diagnostic("error",
                 "value of type {type} cannot act as a context manager",
                 {"type": types.TypePrinter().name(typ)},
diff --git a/artiq/compiler/transforms/llvm_ir_generator.py b/artiq/compiler/transforms/llvm_ir_generator.py
index e85472d22..f057c8b53 100644
--- a/artiq/compiler/transforms/llvm_ir_generator.py
+++ b/artiq/compiler/transforms/llvm_ir_generator.py
@@ -369,6 +369,10 @@ class LLVMIRGenerator:
             llty = ll.FunctionType(lli32, [llptr])
         elif name == "now":
             llty = lli64
+        elif name == "watchdog_set":
+            llty = ll.FunctionType(lli32, [lli32])
+        elif name == "watchdog_clear":
+            llty = ll.FunctionType(llvoid, [lli32])
         else:
             assert False
 
@@ -793,6 +797,12 @@ class LLVMIRGenerator:
             llnow = self.llbuilder.load(llnowptr)
             lladjusted = self.llbuilder.add(llnow, self.map(interval))
             return self.llbuilder.store(lladjusted, llnowptr)
+        elif insn.op == "watchdog_set":
+            interval, = insn.operands
+            return self.llbuilder.call(self.llbuiltin("watchdog_set"), [self.map(interval)])
+        elif insn.op == "watchdog_clear":
+            id, = insn.operands
+            return self.llbuilder.call(self.llbuiltin("watchdog_clear"), [self.map(id)])
         else:
             assert False
 
diff --git a/lit-test/libartiq_support/artiq_time.c b/lit-test/libartiq_support/artiq_time.c
index 1afeadbc0..f60e46e47 100644
--- a/lit-test/libartiq_support/artiq_time.c
+++ b/lit-test/libartiq_support/artiq_time.c
@@ -1,3 +1,15 @@
 #include <stdint.h>
+#include <stdio.h>
 
 int64_t now = 0;
+
+int watchdog_set(int ms)
+{
+  printf("watchdog_set %d\n", ms);
+  return ms;
+}
+
+void watchdog_clear(int id)
+{
+  printf("watchdog_clear %d\n", id);
+}
diff --git a/lit-test/test/codegen/error_illegal_builtin.py b/lit-test/test/codegen/error_illegal_builtin.py
new file mode 100644
index 000000000..ae75ad9b7
--- /dev/null
+++ b/lit-test/test/codegen/error_illegal_builtin.py
@@ -0,0 +1,5 @@
+# RUN: %python -m artiq.compiler.testbench.signature +diag %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+# CHECK-L: ${LINE:+1}: error: builtin function 'watchdog' cannot be used in this context
+watchdog(1.0)
diff --git a/lit-test/test/time/watchdog.py b/lit-test/test/time/watchdog.py
new file mode 100644
index 000000000..b7df4b509
--- /dev/null
+++ b/lit-test/test/time/watchdog.py
@@ -0,0 +1,35 @@
+# RUN: %python -m artiq.compiler.testbench.jit %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+def f():
+    with watchdog(1.0):
+        pass
+
+def g():
+    with watchdog(2.0):
+        raise Exception()
+
+def h():
+    try:
+        g()
+    except:
+        pass
+
+def i():
+    try:
+        with watchdog(3.0):
+            raise Exception()
+    except:
+        pass
+
+# CHECK-L: watchdog_set 1000
+# CHECK-L: watchdog_clear 1000
+f()
+
+# CHECK-L: watchdog_set 2000
+# CHECK-L: watchdog_clear 2000
+h()
+
+# CHECK-L: watchdog_set 3000
+# CHECK-L: watchdog_clear 3000
+i()