diff --git a/Tests/HTMLSelectorTests.m b/Tests/HTMLSelectorTests.m
index a961ca0..af508a8 100644
--- a/Tests/HTMLSelectorTests.m
+++ b/Tests/HTMLSelectorTests.m
@@ -84,7 +84,10 @@ - (void)testNthParsing
     NSArray *nodes = [self.testDoc nodesMatchingSelector:(selectorString)]; \
     NSMutableArray *IDs = [NSMutableArray new]; \
     for (HTMLElement *node in nodes) { \
-        [IDs addObject:(node[@"id"] ?: node.tagName)]; \
+        id object = node[@"id"] ?: node.tagName; \
+        if (object) { \
+            [IDs addObject:(id __nonnull)object]; \
+        } \
     } \
     XCTAssertEqualObjects(IDs, expectedIDs); \
 } while(0)
diff --git a/Tests/HTMLTreeConstructionTests.m b/Tests/HTMLTreeConstructionTests.m
index 8c4bd05..e075798 100644
--- a/Tests/HTMLTreeConstructionTests.m
+++ b/Tests/HTMLTreeConstructionTests.m
@@ -278,8 +278,9 @@ BOOL TreesAreTestEquivalent(id aThing, id bThing)
         if (![bThing isKindOfClass:[HTMLDocumentType class]]) return NO;
         HTMLDocumentType *a = aThing, *b = bThing;
         return (((a.name == nil && b.name == nil) || [a.name isEqualToString:b.name]) &&
-                [a.publicIdentifier isEqualToString:b.publicIdentifier] &&
-                [a.systemIdentifier isEqualToString:b.systemIdentifier]);
+                b.publicIdentifier != nil && b.systemIdentifier != nil &&
+                [a.publicIdentifier isEqualToString:(NSString * __nonnull)b.publicIdentifier] &&
+                [a.systemIdentifier isEqualToString:(NSString * __nonnull)b.systemIdentifier]);
     } else if (arrayLike(aThing)) {
         if (!arrayLike(bThing)) return NO;
         NSArray *a = aThing, *b = bThing;