diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py
index 74040ca54..886f3e92f 100644
--- a/artiq/compiler/transforms/artiq_ir_generator.py
+++ b/artiq/compiler/transforms/artiq_ir_generator.py
@@ -1608,10 +1608,16 @@ class ARTIQIRGenerator(algorithm.Visitor):
                 return self.append(ir.Builtin("round", [arg], node.type))
             else:
                 assert False
-        elif types.is_builtin(typ, "print") or types.is_builtin(typ, "rtio_log"):
+        elif types.is_builtin(typ, "print"):
             self.polymorphic_print([self.visit(arg) for arg in node.args],
-                                   separator=" ", suffix="\n",
-                                   as_rtio=types.is_builtin(typ, "rtio_log"))
+                                   separator=" ", suffix="\n")
+            return ir.Constant(None, builtins.TNone())
+        elif types.is_builtin(typ, "rtio_log"):
+            prefix, *args = node.args
+            self.polymorphic_print([self.visit(prefix)],
+                                   separator=" ", suffix="\x1E", as_rtio=True)
+            self.polymorphic_print([self.visit(arg) for arg in args],
+                                   separator=" ", suffix="\n", as_rtio=True)
             return ir.Constant(None, builtins.TNone())
         elif types.is_builtin(typ, "now"):
             if len(node.args) == 0 and len(node.keywords) == 0:
diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index fd226a7c5..7d109236b 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -753,7 +753,7 @@ class Inferencer(algorithm.Visitor):
                             node.loc, None)
             else:
                 diagnose(valid_forms())
-        elif types.is_builtin(typ, "print") or types.is_builtin(typ, "rtio_log"):
+        elif types.is_builtin(typ, "print"):
             valid_forms = lambda: [
                 valid_form("print(args...) -> None"),
             ]
@@ -766,6 +766,21 @@ class Inferencer(algorithm.Visitor):
                 pass
             else:
                 diagnose(valid_forms())
+        elif types.is_builtin(typ, "rtio_log"):
+            valid_forms = lambda: [
+                valid_form("rtio_log(channel:str, args...) -> None"),
+            ]
+
+            self._unify(node.type, builtins.TNone(),
+                        node.loc, None)
+
+            if len(node.args) >= 1 and len(node.keywords) == 0:
+                arg = node.args[0]
+
+                self._unify(arg.type, builtins.TStr(),
+                            arg.loc, None)
+            else:
+                diagnose(valid_forms())
         elif types.is_builtin(typ, "now"):
             simple_form("now() -> float",
                         [], builtins.TFloat())