diff --git a/QBValidator/QBValidationRangeRule.h b/QBValidator/QBValidationRangeRule.h
index df6d83b..0be3a30 100644
--- a/QBValidator/QBValidationRangeRule.h
+++ b/QBValidator/QBValidationRangeRule.h
@@ -10,8 +10,8 @@
 
 @interface QBValidationRangeRule : QBValidationRule
 
-@property (nonatomic, assign, readonly) NSNumber *minValue;
-@property (nonatomic, assign, readonly) NSNumber *maxValue;
+@property (nonatomic, copy, readonly) NSNumber *minValue;
+@property (nonatomic, copy, readonly) NSNumber *maxValue;
 @property (nonatomic, assign, readonly) BOOL inclusive;
 
 + (instancetype)ruleWithMinValue:(NSNumber *)minValue maxValue:(NSNumber *)maxValue inclusive:(BOOL)inclusive;
diff --git a/QBValidator/QBValidationRangeRule.m b/QBValidator/QBValidationRangeRule.m
index 024a4e0..df25cd0 100644
--- a/QBValidator/QBValidationRangeRule.m
+++ b/QBValidator/QBValidationRangeRule.m
@@ -10,8 +10,8 @@
 
 @interface QBValidationRangeRule ()
 
-@property (nonatomic, assign, readwrite) NSNumber *minValue;
-@property (nonatomic, assign, readwrite) NSNumber *maxValue;
+@property (nonatomic, copy, readwrite) NSNumber *minValue;
+@property (nonatomic, copy, readwrite) NSNumber *maxValue;
 @property (nonatomic, assign, readwrite) BOOL inclusive;
 
 @end