diff --git a/Source/NSKVOInternal.h b/Source/NSKVOInternal.h
index de762d5c0..60b3dd0cf 100644
--- a/Source/NSKVOInternal.h
+++ b/Source/NSKVOInternal.h
@@ -44,13 +44,15 @@
 
 /* This Key Value Observing Implementation is tied to libobjc2 */
 
-#import <Foundation/NSObject.h>
-#import <Foundation/NSString.h>
-#import <Foundation/NSDictionary.h>
-#import <Foundation/NSArray.h>
-#import <Foundation/NSSet.h>
-#import <Foundation/NSKeyValueObserving.h>
-#import <Foundation/NSException.h>
+#import "Foundation/NSObject.h"
+#import "Foundation/NSString.h"
+#import "Foundation/NSDictionary.h"
+#import "Foundation/NSArray.h"
+#import "Foundation/NSSet.h"
+#import "Foundation/NSKeyValueObserving.h"
+#import "Foundation/NSException.h"
+
+#import "GSPrivate.h"
 
 #if defined(__OBJC2__)
 
@@ -114,7 +116,7 @@
 
 // From NSKVOSwizzling
 void
-_NSKVOEnsureKeyWillNotify(id object, NSString *key);
+_NSKVOEnsureKeyWillNotify(id object, NSString *key) GS_ATTRIB_PRIVATE;
 
 #endif
 
diff --git a/Source/NSKVOSupport.m b/Source/NSKVOSupport.m
index 822f3fcc4..2b5f7a381 100644
--- a/Source/NSKVOSupport.m
+++ b/Source/NSKVOSupport.m
@@ -53,7 +53,7 @@
 
 typedef void (^DispatchChangeBlock)(_NSKVOKeyObserver *);
 
-NSString *
+static NSString *
 _NSKVCSplitKeypath(NSString *keyPath, NSString *__autoreleasing *pRemainder)
 {
   NSRange result = [keyPath rangeOfString:@"."];
diff --git a/Source/NSKVOSwizzling.m b/Source/NSKVOSwizzling.m
index 41ebd77e1..283721048 100644
--- a/Source/NSKVOSwizzling.m
+++ b/Source/NSKVOSwizzling.m
@@ -476,7 +476,7 @@ GENERATE_NOTIFYING_SET_IMPL(notifyingSetImplPointer, void *);
       break;                                                                   \
     }
 
-SEL
+static SEL
 KVCSetterForPropertyName(NSObject *self, const char *key)
 {
   SEL    sel = nil;
@@ -649,7 +649,7 @@ _NSKVOEnsureUnorderedCollectionWillNotify(id object, NSString *key,
     }
 }
 
-char *
+static char *
 mutableBufferFromString(NSString *string)
 {
   NSUInteger	lengthInBytes = [string length] + 1;
diff --git a/Source/NSKeyValueCoding+Caching.h b/Source/NSKeyValueCoding+Caching.h
index 024197540..aff3455c1 100644
--- a/Source/NSKeyValueCoding+Caching.h
+++ b/Source/NSKeyValueCoding+Caching.h
@@ -49,6 +49,7 @@
  */
 
 #import "Foundation/NSString.h"
+#import "GSPrivate.h"
 
 id
-valueForKeyWithCaching(id obj, NSString *aKey);
\ No newline at end of file
+valueForKeyWithCaching(id obj, NSString *aKey) GS_ATTRIB_PRIVATE;
diff --git a/Source/NSKeyValueCoding+Caching.m b/Source/NSKeyValueCoding+Caching.m
index 11643c8fa..6a054d268 100644
--- a/Source/NSKeyValueCoding+Caching.m
+++ b/Source/NSKeyValueCoding+Caching.m
@@ -426,7 +426,7 @@ _getBoxedBlockForMethod(NSString *key, Method method, SEL sel, uint64_t version)
 // resolveInstanceMethod:].
 //
 // objc_slot2 has the same struct layout as objc_method.
-Method _Nullable _class_getMethodRecursive(Class aClass, SEL aSelector,
+static Method _Nullable _class_getMethodRecursive(Class aClass, SEL aSelector,
                                            uint64_t *version)
 {
   struct objc_slot2 *slot;
diff --git a/Source/NSURLSessionTask.m b/Source/NSURLSessionTask.m
index 1ca664564..7adc88370 100644
--- a/Source/NSURLSessionTask.m
+++ b/Source/NSURLSessionTask.m
@@ -303,7 +303,7 @@ progress_callback(void *clientp, curl_off_t dltotal, curl_off_t dlnow,
  *
  * libcurl does not unfold HTTP "folded headers" (deprecated since RFC 7230).
  */
-size_t
+static size_t
 header_callback(char *ptr, size_t size, size_t nitems, void *userdata)
 {
   NSURLSessionTask	*task;
@@ -689,7 +689,7 @@ header_callback(char *ptr, size_t size, size_t nitems, void *userdata)
 } /* header_callback */
 
 /* CURLOPT_READFUNCTION: read callback for data uploads */
-size_t
+static size_t
 read_callback(char *buffer, size_t size, size_t nitems, void *userdata)
 {
   NSURLSession 		*session;