diff --git a/BUILD.bazel b/BUILD.bazel
index cd7755e3a7d..05a9b5639b8 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -125,6 +125,7 @@ OPENROAD_COPTS = [
     "-Wformat-security",
     "-Wno-sign-compare",
     "-Wno-unused-parameter",
+    "-Wmismatched-tags",
     "-fopenmp",
 ]
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0909cc0c199..64b2aeaa5a6 100755
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -175,6 +175,7 @@ add_compile_options(
   -ffp-contract=off
   # Apple clang 14.0.0 deprecates sprintf, which generates 900 warnings.
   $<$<CXX_COMPILER_ID:AppleClang>:-Wno-deprecated-declarations>
+  $<$<CXX_COMPILER_ID:AppleClang>:-Wmismatched-tags>
   $<$<BOOL:${ASAN}>:-fsanitize=address>
   $<$<BOOL:${ASAN}>:-fno-omit-frame-pointer>
   $<$<BOOL:${ASAN}>:-g>
diff --git a/src/odb/include/odb/3dblox.h b/src/odb/include/odb/3dblox.h
index 34da65af946..59e17000023 100644
--- a/src/odb/include/odb/3dblox.h
+++ b/src/odb/include/odb/3dblox.h
@@ -16,12 +16,7 @@ class Sta;
 }
 namespace odb {
 class dbDatabase;
-class ChipletDef;
-class ChipletRegion;
 class dbChip;
-class ChipletInst;
-class Connection;
-class DesignDef;
 class dbChipRegionInst;
 class dbChipInst;
 class dbChipRegion;
@@ -31,6 +26,11 @@ class dbInst;
 class dbTech;
 class dbLib;
 
+struct ChipletDef;
+struct ChipletRegion;
+struct ChipletInst;
+struct Connection;
+struct DesignDef;
 struct BumpMapEntry;
 
 class ThreeDBlox
diff --git a/src/par/include/par/PartitionMgr.h b/src/par/include/par/PartitionMgr.h
index edea19ae53e..9f75c6c22cc 100644
--- a/src/par/include/par/PartitionMgr.h
+++ b/src/par/include/par/PartitionMgr.h
@@ -46,7 +46,7 @@ struct MasterInfo
 
 class Cluster;
 using SharedClusterVector = std::vector<std::shared_ptr<Cluster>>;
-class ModuleMgr;
+struct ModuleMgr;
 class TritonPart;
 
 struct CompareInstancePtr