diff --git a/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp b/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
index 1cc16de4f08f..a36b25f170ff 100644
--- a/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
+++ b/lib/Dialect/FIRRTL/Transforms/LowerClasses.cpp
@@ -384,16 +384,14 @@ PathTracker::getOrComputeNeedsAltBasePath(Location loc, StringAttr moduleName,
       break;
     }
     // If there is more than one instance of this module, then the path
-    // operation is ambiguous, which is a warning.  This should become an error
-    // once user code is properly enforcing single instantiation, but in
-    // practice this generates the same outputs as the original flow for now.
-    // See https://github.com/llvm/circt/issues/7128.
+    // operation is ambiguous, which is an error.
     if (!node->hasOneUse()) {
-      auto diag = mlir::emitWarning(loc)
+      auto diag = mlir::emitError(loc)
                   << "unable to uniquely resolve target due "
                      "to multiple instantiation";
       for (auto *use : node->uses())
         diag.attachNote(use->getInstance().getLoc()) << "instance here";
+      return diag;
     }
     node = (*node->usesBegin())->getParent();
   }
@@ -534,10 +532,8 @@ PathTracker::processPathTrackers(const AnnoTarget &target) {
       if (node->getModule() == owningModule || node->noUses())
         break;
 
-      // Append the next level of hierarchy to the path. Note that if there
-      // are multiple instances, which we warn about, this is where the
-      // ambiguity manifests. In practice, just picking usesBegin generates
-      // the same output as EmitOMIR would for now.
+      // Append the next level of hierarchy to the path.
+      assert(node->hasOneUse() && "expected single instantiation");
       InstanceRecord *inst = *node->usesBegin();
       path.push_back(
           OpAnnoTarget(inst->getInstance<InstanceOp>())
diff --git a/lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp b/lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp
index a98de8492366..2ed6c01f9827 100644
--- a/lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp
+++ b/lib/Dialect/FIRRTL/Transforms/ResolvePaths.cpp
@@ -58,15 +58,13 @@ struct PathResolver {
                << "unable to resolve path relative to owning module "
                << owningModule.getModuleNameAttr();
       // If there is more than one instance of this module, then the path
-      // operation is ambiguous, which is a warning. This should become an error
-      // once user code is properly enforcing single instantiation, but in
-      // practice this generates the same outputs as the original flow for now.
-      // See https://github.com/llvm/circt/issues/7128.
+      // operation is ambiguous, which is an error.
       if (!node->hasOneUse()) {
-        auto diag = emitWarning(loc) << "unable to uniquely resolve target due "
-                                        "to multiple instantiation";
+        auto diag = emitError(loc) << "unable to uniquely resolve target due "
+                                      "to multiple instantiation";
         for (auto *use : node->uses())
           diag.attachNote(use->getInstance().getLoc()) << "instance here";
+        return diag;
       }
       node = (*node->usesBegin())->getParent();
     }
diff --git a/test/Dialect/FIRRTL/resolve-paths-errors.mlir b/test/Dialect/FIRRTL/resolve-paths-errors.mlir
index 9baee2194bc6..d8bf3c3e3b4e 100644
--- a/test/Dialect/FIRRTL/resolve-paths-errors.mlir
+++ b/test/Dialect/FIRRTL/resolve-paths-errors.mlir
@@ -74,7 +74,7 @@ firrtl.module @VectorTarget(in %a : !firrtl.vector<uint<1>, 1>) {
 
 firrtl.circuit "AmbiguousPath" {
 firrtl.module @AmbiguousPath() {
-    // expected-warning @below {{unable to uniquely resolve target due to multiple instantiation}}
+    // expected-error @below {{unable to uniquely resolve target due to multiple instantiation}}
     %0 = firrtl.unresolved_path "OMReferenceTarget:~AmbiguousPath|Child"
     // expected-note @below {{instance here}}
     firrtl.instance child0 @Child()
diff --git a/test/Dialect/FIRRTL/resolve-paths.mlir b/test/Dialect/FIRRTL/resolve-paths.mlir
index 6664d917a649..80d97288f3d4 100644
--- a/test/Dialect/FIRRTL/resolve-paths.mlir
+++ b/test/Dialect/FIRRTL/resolve-paths.mlir
@@ -225,58 +225,3 @@ firrtl.class @OM() {
     %0 = firrtl.unresolved_path "OMReferenceTarget:~TargetWire|TargetWire>wire"
 }
 }
-
-// -----
-
-// CHECK-LABEL: firrtl.circuit "AmbiguousLocalPath"
-firrtl.circuit "AmbiguousLocalPath" {
-firrtl.module @AmbiguousLocalPath() {
-  // CHECK: [[PATH0:%.+]] = firrtl.path reference distinct[[[DISTINCT0:.+]]]<>
-  %0 = firrtl.unresolved_path "OMReferenceTarget:~AmbiguousLocalPath|Child"
-
-  // CHECK: firrtl.list.create [[PATH0]]
-  %1 = firrtl.list.create %0 : !firrtl.list<path>
-
-  // CHECK: firrtl.instance child0
-  firrtl.instance child0 @Child()
-  // CHECK: firrtl.instance child1
-  firrtl.instance child1 @Child()
-}
-// CHECK: firrtl.module @Child
-// CHECK-SAME: {class = "circt.tracker", id = distinct[[[DISTINCT0]]]<>}
-firrtl.module @Child() {}
-}
-
-// -----
-
-// CHECK-LABEL: firrtl.circuit "AmbiguousNonLocalPath"
-firrtl.circuit "AmbiguousNonLocalPath" {
-// CHECK: hw.hierpath private [[NLA:@.+]] [@Child2::[[SYM0:@.+]], @Child3::[[SYM1:@.+]], @Child4]
-firrtl.module @AmbiguousNonLocalPath() {
-  // CHECK: [[PATH0:%.+]] = firrtl.path reference distinct[[[DISTINCT0:.+]]]<>
-  %0 = firrtl.unresolved_path "OMReferenceTarget:~AmbiguousNonLocalPath|Child2/child3:Child3/child4:Child4"
-
-  // CHECK: firrtl.list.create [[PATH0]]
-  %1 = firrtl.list.create %0 : !firrtl.list<path>
-
-  // CHECK: firrtl.instance child1
-  firrtl.instance child1 @Child1()
-}
-firrtl.module @Child1() {
-  // CHECK: firrtl.instance child2_0
-  firrtl.instance child2_0 @Child2()
-  // CHECK: firrtl.instance child2_1
-  firrtl.instance child2_1 @Child2()
-}
-firrtl.module @Child2() {
-  // CHECK: firrtl.instance child3 sym [[SYM0]]
-  firrtl.instance child3 @Child3()
-}
-firrtl.module @Child3() {
-  // CHECK: firrtl.instance child4 sym [[SYM1]]
-  firrtl.instance child4 @Child4()
-}
-// CHECK: firrtl.module @Child4
-// CHECK-SAME: {circt.nonlocal = [[NLA]], class = "circt.tracker", id = distinct[[[DISTINCT0]]]<>}
-firrtl.module @Child4() {}
-}