diff --git a/src/snl/snl/kernel/SNLAttributes.cpp b/src/snl/snl/kernel/SNLAttributes.cpp
index 48c7cf2a..dd7ceb0e 100644
--- a/src/snl/snl/kernel/SNLAttributes.cpp
+++ b/src/snl/snl/kernel/SNLAttributes.cpp
@@ -129,6 +129,11 @@ bool SNLAttributes::compareAttributes(
   std::string& reason) {
   auto prop1 = SNLAttributesPrivateProperty::get(object1);
   auto prop2 = SNLAttributesPrivateProperty::get(object2);
+  //xor
+  if ((prop1 and not prop2) or (not prop1 and prop2)) {
+    reason = "attributes property mismatch";
+    return false;
+  }
   if (prop1 and prop2) {
     using Attributes = std::vector<SNLAttribute>;
     Attributes attributes1(
diff --git a/test/snl/snl/kernel/SNLAttributesTest.cpp b/test/snl/snl/kernel/SNLAttributesTest.cpp
index dafff097..09bc1d39 100644
--- a/test/snl/snl/kernel/SNLAttributesTest.cpp
+++ b/test/snl/snl/kernel/SNLAttributesTest.cpp
@@ -91,4 +91,39 @@ TEST_F(SNLAttributesTest, testCreationOnDesignObject) {
 
   SNLAttributes::clearAttributes(term);
   EXPECT_TRUE(SNLAttributes::getAttributes(term).empty());
+}
+
+TEST_F(SNLAttributesTest, testCompare) {
+  auto design1 = SNLDesign::create(library_, SNLName("DESIGN1"));
+  auto design2 = SNLDesign::create(library_, SNLName("DESIGN2"));
+  std::string reason;
+  EXPECT_TRUE(SNLAttributes::compareAttributes(design1, design2, reason));
+  EXPECT_TRUE(reason.empty());
+
+  SNLAttributes::addAttribute(design1,
+    SNLAttributes::SNLAttribute(
+      SNLName("PRAGMA1"),
+      SNLAttributes::SNLAttribute::Value("value1")));
+  EXPECT_FALSE(SNLAttributes::compareAttributes(design1, design2, reason));
+  EXPECT_FALSE(reason.empty());
+
+  SNLAttributes::addAttribute(design2,
+    SNLAttributes::SNLAttribute(
+      SNLName("PRAGMA1"),
+      SNLAttributes::SNLAttribute::Value("value1")));
+  reason = std::string();
+  EXPECT_TRUE(SNLAttributes::compareAttributes(design1, design2, reason));
+  EXPECT_TRUE(reason.empty());
+
+  SNLAttributes::addAttribute(design1,
+    SNLAttributes::SNLAttribute(
+      SNLName("PRAGMA2"),
+      SNLAttributes::SNLAttribute::Value("value2")));
+  SNLAttributes::addAttribute(design2,
+    SNLAttributes::SNLAttribute(
+      SNLName("PRAGMA2"),
+      SNLAttributes::SNLAttribute::Value("value3")));
+  reason = std::string();
+  EXPECT_FALSE(SNLAttributes::compareAttributes(design1, design2, reason));
+  EXPECT_FALSE(reason.empty());
 }
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