diff --git a/lib/Dialect/ESI/ESIDialect.cpp b/lib/Dialect/ESI/ESIDialect.cpp
index 32c9e39e3a..4fcc95bca8 100644
--- a/lib/Dialect/ESI/ESIDialect.cpp
+++ b/lib/Dialect/ESI/ESIDialect.cpp
@@ -41,14 +41,11 @@ void ESIDialect::initialize() {
 
 Operation *ESIDialect::materializeConstant(OpBuilder &builder, Attribute value,
                                            Type type, Location loc) {
-  // Integer constants.
-  if (auto intType = dyn_cast<IntegerType>(type))
-    if (auto attrValue = dyn_cast<IntegerAttr>(value))
-      return builder.create<hw::ConstantOp>(loc, attrValue.getType(),
-                                            attrValue);
   if (isa<mlir::UnitAttr>(value))
     return builder.create<hw::ConstantOp>(loc, builder.getI1Type(), 1);
-  return nullptr;
+  return builder.getContext()
+      ->getOrLoadDialect<hw::HWDialect>()
+      ->materializeConstant(builder, value, type, loc);
 }
 
 // Provide implementations for the enums we use.
diff --git a/lib/Dialect/ESI/ESIFolds.cpp b/lib/Dialect/ESI/ESIFolds.cpp
index b7cd4ac95c..11505d81b7 100644
--- a/lib/Dialect/ESI/ESIFolds.cpp
+++ b/lib/Dialect/ESI/ESIFolds.cpp
@@ -19,8 +19,10 @@ LogicalResult WrapValidReadyOp::fold(FoldAdaptor,
                                      SmallVectorImpl<OpFoldResult> &results) {
   if (!getChanOutput().getUsers().empty())
     return failure();
-  results.push_back(NullChannelAttr::get(
-      getContext(), TypeAttr::get(getChanOutput().getType())));
+  OpBuilder builder(getContext());
+  results.push_back(
+      builder.create<NullSourceOp>(getLoc(), getChanOutput().getType())
+          .getOut());
   results.push_back(IntegerAttr::get(IntegerType::get(getContext(), 1), 1));
   return success();
 }
@@ -44,22 +46,30 @@ LogicalResult UnwrapFIFOOp::canonicalize(UnwrapFIFOOp op,
 
 LogicalResult WrapFIFOOp::fold(FoldAdaptor,
                                SmallVectorImpl<OpFoldResult> &results) {
-  if (getChanOutput().getUsers().empty()) {
-    results.push_back({});
-    results.push_back(IntegerAttr::get(
-        IntegerType::get(getContext(), 1, IntegerType::Signless), 0));
-    return success();
-  }
-  return failure();
+  if (!getChanOutput().getUsers().empty())
+    return failure();
+
+  OpBuilder builder(getContext());
+  results.push_back(
+      builder.create<NullSourceOp>(getLoc(), getChanOutput().getType())
+          .getOut());
+  results.push_back(IntegerAttr::get(
+      IntegerType::get(getContext(), 1, IntegerType::Signless), 0));
+  return success();
 }
 
 LogicalResult WrapFIFOOp::canonicalize(WrapFIFOOp op,
                                        PatternRewriter &rewriter) {
-  auto unwrap =
-      dyn_cast_or_null<UnwrapFIFOOp>(*op.getChanOutput().getUsers().begin());
+
+  if (!op.getChanOutput().hasOneUse())
+    return rewriter.notifyMatchFailure(
+        op, "channel output doesn't have exactly one use");
+  auto unwrap = dyn_cast_or_null<UnwrapFIFOOp>(
+      op.getChanOutput().getUses().begin()->getOwner());
   if (succeeded(UnwrapFIFOOp::mergeAndErase(unwrap, op, rewriter)))
     return success();
-  return failure();
+  return rewriter.notifyMatchFailure(
+      op, "could not find corresponding unwrap for wrap");
 }
 
 OpFoldResult WrapWindow::fold(FoldAdaptor) {
diff --git a/test/Dialect/ESI/canonicalizers.mlir b/test/Dialect/ESI/canonicalizers.mlir
new file mode 100644
index 0000000000..6ad6a24a08
--- /dev/null
+++ b/test/Dialect/ESI/canonicalizers.mlir
@@ -0,0 +1,15 @@
+// RUN: circt-opt %s --canonicalize | FileCheck %s
+
+// CHECK-LABEL:  hw.module @TestDanglingFIFO() {
+// CHECK-NEXT:     hw.output
+hw.module @TestDanglingFIFO() {
+  %c0 = hw.constant 0 : i1
+  %chanOutput, %ready = esi.wrap.fifo %c0, %c0 : !esi.channel<i1, FIFO>
+}
+
+// CHECK-LABEL:  hw.module @TestDanglingValidReady() {
+// CHECK-NEXT:     hw.output
+hw.module @TestDanglingValidReady() {
+  %c0 = hw.constant 0 : i1
+  %chanOutput, %ready = esi.wrap.vr %c0, %c0 : i1
+}