diff --git a/CompactConstraint/NSLayoutConstraint+CompactConstraint.h b/CompactConstraint/NSLayoutConstraint+CompactConstraint.h
index c0b620e..2582cbf 100644
--- a/CompactConstraint/NSLayoutConstraint+CompactConstraint.h
+++ b/CompactConstraint/NSLayoutConstraint+CompactConstraint.h
@@ -3,6 +3,8 @@
 //  Copyright (c) 2014 Marco Arment. See included LICENSE file.
 //
 
+#import "TargetConditionals.h" 
+
 #if TARGET_OS_IPHONE
 #import <UIKit/UIKit.h>
 #else
diff --git a/CompactConstraint/NSLayoutConstraint+CompactConstraint.m b/CompactConstraint/NSLayoutConstraint+CompactConstraint.m
index b3edabb..b627023 100644
--- a/CompactConstraint/NSLayoutConstraint+CompactConstraint.m
+++ b/CompactConstraint/NSLayoutConstraint+CompactConstraint.m
@@ -3,6 +3,8 @@
 //  Copyright (c) 2014 Marco Arment. See included LICENSE file.
 //
 
+#import "TargetConditionals.h" 
+
 #if TARGET_OS_IPHONE
 #define kPriorityRequired UILayoutPriorityRequired
 #else
@@ -49,6 +51,7 @@ + (NSArray *)identifiedConstraintsWithVisualFormat:(NSString *)format options:(N
 // For release builds, where the asserted variables (leftOperandScanned, etc.) aren't used because the assertions are removed
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-variable"
+#pragma clang diagnostic ignored "-Wunused-value"
 
 + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary *)metrics views:(NSDictionary *)views self:(id)selfView
 {
@@ -117,6 +120,7 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
     NSString *identifier = relationship;
 
     BOOL leftOperandScanned = [scanner scanUpToCharactersFromSet:leftOperandTerminatingCharacterSet intoString:&leftOperandStr];
+    #pragma unused(leftOperandScanned)
     NSAssert(leftOperandScanned, @"No left operand given");
     leftOperandStr = [leftOperandStr stringByTrimmingCharactersInSet:leftOperandTerminatingCharacterSet];
     NSRange lastDot = [leftOperandStr rangeOfString:@"." options:NSBackwardsSearch];
@@ -135,6 +139,7 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
     leftAttribute = (NSLayoutAttribute) [leftAttributeNumber integerValue];
 
     BOOL operatorScanned = [scanner scanCharactersFromSet:operatorCharacterSet intoString:&operatorStr];
+    #pragma unused(operatorScanned)
     NSAssert(operatorScanned, @"No operator given");
     NSLayoutRelation relation;
     if ([operatorStr isEqualToString:@"=="] || [operatorStr isEqualToString:@"="]) relation = NSLayoutRelationEqual;
@@ -150,6 +155,7 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
         // right operand is a symbol. Either a metric or a view. Views have dot-properties, metrics don't.
         BOOL rightOperandScanned = [scanner scanUpToCharactersFromSet:rightOperandTerminatingCharacterSet intoString:&rightOperandStr];
         NSAssert(rightOperandScanned, @"No right operand given");
+        #pragma unused(rightOperandScanned)
 
         lastDot = [rightOperandStr rangeOfString:@"." options:NSBackwardsSearch];
         if (lastDot.location == NSNotFound) {
@@ -198,6 +204,8 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
             // see if the scalar is a metric instead of a literal number
             BOOL scalarAfterMultiplication = [scanner scanUpToCharactersFromSet:rightOperandTerminatingCharacterSet intoString:&rightValueStr];
             NSAssert(scalarAfterMultiplication, @"No scalar given after '*' on right side");
+            #pragma unused(scalarAfterMultiplication)
+
             rightMetricNumber = metrics[rightValueStr];
             NSAssert1(rightMetricNumber, @"Right scalar '%@' not found in metrics dictionary", rightValueStr);
             rightScalar = [rightMetricNumber doubleValue];
@@ -211,6 +219,8 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
             // see if the scalar is a metric instead of a literal number
             BOOL constantAfterAddition = [scanner scanUpToCharactersFromSet:rightOperandTerminatingCharacterSet intoString:&rightValueStr];
             NSAssert(constantAfterAddition, @"No constant given after '+' on right side");
+            #pragma unused(constantAfterAddition)
+
             rightMetricNumber = metrics[rightValueStr];
             NSAssert1(rightMetricNumber, @"Right constant '%@' not found in metrics dictionary", rightValueStr);
             rightConstant = [rightMetricNumber doubleValue];
@@ -229,6 +239,8 @@ + (instancetype)compactConstraint:(NSString *)relationship metrics:(NSDictionary
             // see if the priority is a metric instead of a literal number
             BOOL priorityAfterAt = [scanner scanUpToCharactersFromSet:rightOperandTerminatingCharacterSet intoString:&rightValueStr];
             NSAssert(priorityAfterAt, @"No priority given after '@' on right side");
+            #pragma unused(priorityAfterAt)
+
             rightMetricNumber = metrics[rightValueStr];
             NSAssert1(rightMetricNumber, @"Right priority '%@' not found in metrics dictionary", rightValueStr);
             priority = [rightMetricNumber doubleValue];
diff --git a/README.md b/README.md
index 9d98a50..18fd24e 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@ CompactConstraint syntax maps directly to the paramters passed to NSLayoutConstr
 
 `leftItem` and `rightItem` are keys from the supplied `views` dictionary that map to UIViews, just like with Apple's visual-format-language calls.
 
-`rightItem` may be "super", which is interpreted as `leftItem`'s superview. If you specify a `@"super"` key in `views`, your supplied value will be used instead.
+`rightItem` may be "super", which is interpreted as `leftItem`'s superview, or "safe", which is interpreted as `leftItem`'s superview's `safeAreaLayoutGuide`. If you specify `@"super"` or `@"safe"` keys in `views`, your supplied values will be used instead.
 
 `multiplier`, `constant`, `priority`, and `identifier` are optional. Additionally, `rightItem.attribute`, `multiplier`, `constant`, and `priority` can all optionally be replaced by entries in the supplied `metrics` dictionary, mapping to NSNumbers.