diff --git a/ObjectiveGit/GTConfiguration+Private.h b/ObjectiveGit/GTConfiguration+Private.h
index b33b1e700..efd0598ec 100644
--- a/ObjectiveGit/GTConfiguration+Private.h
+++ b/ObjectiveGit/GTConfiguration+Private.h
@@ -18,6 +18,6 @@
 /// repository - The repository in which the config resides. May be nil.
 ///
 /// Returns the initialized object.
-- (nullable instancetype)initWithGitConfig:(git_config *)config repository:(nullable GTRepository *)repository NS_DESIGNATED_INITIALIZER;
+- (nullable instancetype)initWithGitConfig:(nonnull git_config *)config repository:(nullable GTRepository *)repository NS_DESIGNATED_INITIALIZER;
 
 @end
diff --git a/ObjectiveGit/GTDiff+Private.h b/ObjectiveGit/GTDiff+Private.h
index 38ecb2a1d..03b7f9146 100644
--- a/ObjectiveGit/GTDiff+Private.h
+++ b/ObjectiveGit/GTDiff+Private.h
@@ -14,6 +14,6 @@
 /// provides a pointer to that structure to the given `block`.
 ///
 /// Returns the result of invoking `block`.
-+ (int)handleParsedOptionsDictionary:(nullable NSDictionary *)dictionary usingBlock:(int (^)(git_diff_options *optionsStruct))block;
++ (int)handleParsedOptionsDictionary:(nullable NSDictionary *)dictionary usingBlock:(nonnull int (^)(git_diff_options * __null_unspecified optionsStruct))block;
 
 @end
diff --git a/ObjectiveGit/GTFilter.h b/ObjectiveGit/GTFilter.h
index 33fea06f0..8f70cc5e3 100644
--- a/ObjectiveGit/GTFilter.h
+++ b/ObjectiveGit/GTFilter.h
@@ -34,7 +34,7 @@ extern const NSInteger GTFilterErrorNameAlreadyRegistered;
 
 /// The check block. Determines whether the `applyBlock` should be run for given
 /// source.
-@property (nonatomic, copy) BOOL (^checkBlock)(void **payload, GTFilterSource *source, const char **attr_values);
+@property (nonatomic, copy) BOOL (^checkBlock)(void * __null_unspecified * __null_unspecified payload, GTFilterSource *source,  const char * __null_unspecified * __null_unspecified attr_values);
 
 /// The cleanup block. Called after the `applyBlock` to given the filter a
 /// chance to clean up the `payload`.
@@ -49,7 +49,7 @@ extern const NSInteger GTFilterErrorNameAlreadyRegistered;
 /// applyBlock - The block to use to apply the filter. Cannot be nil.
 ///
 /// Returns the initialized object.
-- (nullable instancetype)initWithName:(NSString *)name attributes:(nullable NSString *)attributes applyBlock:(NSData * (^)(void **payload, NSData *from, GTFilterSource *source, BOOL *applied))applyBlock NS_DESIGNATED_INITIALIZER;
+- (nullable instancetype)initWithName:(NSString *)name attributes:(nullable NSString *)attributes applyBlock:(NSData * (^)(void *__null_unspecified * __null_unspecified payload, NSData *from, GTFilterSource *source, BOOL *applied))applyBlock NS_DESIGNATED_INITIALIZER;
 
 /// Look up a filter based on its name.
 ///
diff --git a/ObjectiveGit/GTReflog+Private.h b/ObjectiveGit/GTReflog+Private.h
index 9fc78e8b8..19fc16b9f 100644
--- a/ObjectiveGit/GTReflog+Private.h
+++ b/ObjectiveGit/GTReflog+Private.h
@@ -12,13 +12,13 @@
 
 @interface GTReflog ()
 
-- (instancetype)init NS_UNAVAILABLE;
+- (nullable instancetype)init NS_UNAVAILABLE;
 
 /// Initializes the receiver with a reference. Designated initializer.
 ///
 /// reference - The reference whose reflog is being represented. Cannot be nil.
 ///
 /// Returns the initialized object.
-- (nullable instancetype)initWithReference:(GTReference *)reference NS_DESIGNATED_INITIALIZER;
+- (nullable instancetype)initWithReference:(nonnull GTReference *)reference NS_DESIGNATED_INITIALIZER;
 
 @end