diff --git a/FBRetainCycleDetector/Layout/Classes/FBClassStrongLayout.mm b/FBRetainCycleDetector/Layout/Classes/FBClassStrongLayout.mm
index a1feacf..f377021 100644
--- a/FBRetainCycleDetector/Layout/Classes/FBClassStrongLayout.mm
+++ b/FBRetainCycleDetector/Layout/Classes/FBClassStrongLayout.mm
@@ -146,7 +146,8 @@ static NSUInteger FBGetMinimumIvarIndex(__unsafe_unretained Class aCls) {
   if (count > 0) {
     Ivar ivar = ivars[0];
     ptrdiff_t offset = ivar_getOffset(ivar);
-    minimumIndex = offset / (sizeof(void *));
+    // unaligned bytes at the start of this class's ivars are not represented in the layout bitmap.
+    minimumIndex = (offset + (sizeof(void *) - 1)) / (sizeof(void *));
   }
 
   free(ivars);
diff --git a/FBRetainCycleDetectorTests/FBClassStrongLayoutTests.mm b/FBRetainCycleDetectorTests/FBClassStrongLayoutTests.mm
index 07ac1d5..d2bbe6d 100644
--- a/FBRetainCycleDetectorTests/FBClassStrongLayoutTests.mm
+++ b/FBRetainCycleDetectorTests/FBClassStrongLayoutTests.mm
@@ -13,6 +13,7 @@
 
 #import <FBRetainCycleDetector/FBClassStrongLayout.h>
 #import <FBRetainCycleDetector/FBRetainCycleDetector.h>
+#import <FBRetainCycleDetector/FBObjectReference.h>
 
 @interface _RCDTestEmptyClass : NSObject
 @end
@@ -157,6 +158,22 @@ @implementation _RCDTestClassWithCppStructAndStrongProperty
 }
 @end
 
+@interface _RCDTestClassWithUnalignEndIvar : NSObject {
+  char content[20];
+}
+@end
+@implementation _RCDTestClassWithUnalignEndIvar
+@end
+
+@interface _RCDTestClassWithUnalignEndIvarParentClass : _RCDTestClassWithUnalignEndIvar {
+  int integer;
+  __weak NSObject *object1;
+  NSObject *object2;
+}
+@end
+@implementation _RCDTestClassWithUnalignEndIvarParentClass
+@end
+
 @interface FBClassStrongLayoutTests : XCTestCase
 @end
 
@@ -260,4 +277,11 @@ - (void)testLayoutForClassWithCppStructAndStrongPropertyWillNotCrashAndFetchStro
   XCTAssertEqual([ivars count], 1);
 }
 
+- (void)testLayoutForClassWithParentClassHasUnalignEndIvar
+{
+  NSArray<id<FBObjectReference>> *ivars = FBGetObjectStrongReferences([_RCDTestClassWithUnalignEndIvarParentClass new], nil);
+  XCTAssertEqual([ivars count], 1);
+  XCTAssertEqualObjects([[ivars firstObject] namePath], @[@"object2"]);
+}
+
 @end