diff --git a/artiq/compiler/module.py b/artiq/compiler/module.py
index 052a176ac..c19d6d0ac 100644
--- a/artiq/compiler/module.py
+++ b/artiq/compiler/module.py
@@ -64,8 +64,8 @@ class Module:
         interleaver = transforms.Interleaver(engine=self.engine)
         invariant_detection = analyses.InvariantDetection(engine=self.engine)
 
-        cast_monomorphizer.visit(src.typedtree)
         int_monomorphizer.visit(src.typedtree)
+        cast_monomorphizer.visit(src.typedtree)
         inferencer.visit(src.typedtree)
         monomorphism_validator.visit(src.typedtree)
         escape_validator.visit(src.typedtree)
diff --git a/artiq/compiler/transforms/cast_monomorphizer.py b/artiq/compiler/transforms/cast_monomorphizer.py
index 50e2bda4f..8e373ab1e 100644
--- a/artiq/compiler/transforms/cast_monomorphizer.py
+++ b/artiq/compiler/transforms/cast_monomorphizer.py
@@ -18,6 +18,7 @@ class CastMonomorphizer(algorithm.Visitor):
                 types.is_builtin(node.func.type, "int64")):
             typ = node.type.find()
             if (not types.is_var(typ["width"]) and
+                    len(node.args) == 1 and
                     builtins.is_int(node.args[0].type) and
                     types.is_var(node.args[0].type.find()["width"])):
                 if isinstance(node.args[0], asttyped.BinOpT):
diff --git a/artiq/test/lit/monomorphism/bug_1242.py b/artiq/test/lit/monomorphism/bug_1242.py
new file mode 100644
index 000000000..8918a30cc
--- /dev/null
+++ b/artiq/test/lit/monomorphism/bug_1242.py
@@ -0,0 +1,8 @@
+# RUN: %python -m artiq.compiler.testbench.signature %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+x = 0x100000000
+# CHECK-L: x: numpy.int64
+
+y = int32(x)
+# CHECK-L: y: numpy.int32