diff --git a/ReactiveObjC/RACSequence.h b/ReactiveObjC/RACSequence.h
index e807a05d3..c7bc6b9a9 100644
--- a/ReactiveObjC/RACSequence.h
+++ b/ReactiveObjC/RACSequence.h
@@ -259,7 +259,7 @@ typedef RACSequence * _Nullable (^RACSequenceBindBlock)(ValueType _Nullable valu
 ///               return value must be an object. This argument cannot be nil.
 ///
 /// Returns a new sequence of reduced tuple values.
-- (RACSequence *)reduceEach:(id _Nullable (^)())reduceBlock;
+- (RACSequence *)reduceEach:(RACReduceBlock)reduceBlock;
 
 /// Returns a sequence consisting of `value`, followed by the values in the
 /// receiver.
@@ -309,7 +309,7 @@ typedef RACSequence * _Nullable (^RACSequenceBindBlock)(ValueType _Nullable valu
 ///
 /// Returns a new sequence containing the results from each invocation of
 /// `reduceBlock`.
-+ (RACSequence<ValueType> *)zip:(id<NSFastEnumeration>)sequences reduce:(id _Nullable (^)())reduceBlock;
++ (RACSequence<ValueType> *)zip:(id<NSFastEnumeration>)sequences reduce:(RACReduceBlock)reduceBlock;
 
 /// Returns a sequence obtained by concatenating `sequences` in order.
 + (RACSequence<ValueType> *)concat:(id<NSFastEnumeration>)sequences;
diff --git a/ReactiveObjC/RACSignal+Operations.h b/ReactiveObjC/RACSignal+Operations.h
index d2e178264..3c9ef0460 100644
--- a/ReactiveObjC/RACSignal+Operations.h
+++ b/ReactiveObjC/RACSignal+Operations.h
@@ -197,7 +197,8 @@ extern const NSInteger RACSignalErrorNoMatchingCase;
 ///
 /// Returns a signal which sends the results from each invocation of
 /// `reduceBlock`.
-+ (RACSignal<ValueType> *)combineLatest:(id<NSFastEnumeration>)signals reduce:(ValueType _Nullable (^)())reduceBlock RAC_WARN_UNUSED_RESULT;
++ (RACSignal<ValueType> *)combineLatest:(id<NSFastEnumeration>)signals reduce:(RACGenericReduceBlock)reduceBlock RAC_WARN_UNUSED_RESULT;
+
 
 /// Merges the receiver and the given signal with `+merge:` and returns the
 /// resulting signal.
diff --git a/ReactiveObjC/RACSignal+Operations.m b/ReactiveObjC/RACSignal+Operations.m
index ec250a490..dbc4df773 100644
--- a/ReactiveObjC/RACSignal+Operations.m
+++ b/ReactiveObjC/RACSignal+Operations.m
@@ -456,7 +456,7 @@ + (RACSignal *)combineLatest:(id<NSFastEnumeration>)signals {
 	}] setNameWithFormat:@"+combineLatest: %@", signals];
 }
 
-+ (RACSignal *)combineLatest:(id<NSFastEnumeration>)signals reduce:(id (^)())reduceBlock {
++ (RACSignal *)combineLatest:(id<NSFastEnumeration>)signals reduce:(RACGenericReduceBlock)reduceBlock {
 	NSCParameterAssert(reduceBlock != nil);
 
 	RACSignal *result = [self combineLatest:signals];
diff --git a/ReactiveObjC/RACSignal.h b/ReactiveObjC/RACSignal.h
index 6fb5e03fe..1d4670e70 100644
--- a/ReactiveObjC/RACSignal.h
+++ b/ReactiveObjC/RACSignal.h
@@ -218,7 +218,7 @@ typedef RACSignal * _Nullable (^RACSignalBindBlock)(ValueType _Nullable value, B
 ///               return value must be an object. This argument cannot be nil.
 ///
 /// Returns a new signal of reduced tuple values.
-- (RACSignal *)reduceEach:(id _Nullable (^)())reduceBlock RAC_WARN_UNUSED_RESULT;
+- (RACSignal *)reduceEach:(RACReduceBlock)reduceBlock RAC_WARN_UNUSED_RESULT;
 
 /// Returns a signal consisting of `value`, followed by the values in the
 /// receiver.
@@ -268,7 +268,7 @@ typedef RACSignal * _Nullable (^RACSignalBindBlock)(ValueType _Nullable value, B
 ///
 /// Returns a new signal containing the results from each invocation of
 /// `reduceBlock`.
-+ (RACSignal<ValueType> *)zip:(id<NSFastEnumeration>)signals reduce:(id _Nullable (^)())reduceBlock RAC_WARN_UNUSED_RESULT;
++ (RACSignal<ValueType> *)zip:(id<NSFastEnumeration>)signals reduce:(RACGenericReduceBlock)reduceBlock RAC_WARN_UNUSED_RESULT;
 
 /// Returns a signal obtained by concatenating `signals` in order.
 + (RACSignal<ValueType> *)concat:(id<NSFastEnumeration>)signals RAC_WARN_UNUSED_RESULT;
diff --git a/ReactiveObjC/RACStream.h b/ReactiveObjC/RACStream.h
index 0ae04de17..b397d18b4 100644
--- a/ReactiveObjC/RACStream.h
+++ b/ReactiveObjC/RACStream.h
@@ -21,6 +21,12 @@ NS_ASSUME_NONNULL_BEGIN
 /// to be overridden.
 @interface RACStream<__covariant ValueType> : NSObject
 
+_Pragma("clang diagnostic push") \
+_Pragma("clang diagnostic ignored \"-Wstrict-prototypes\"") \
+typedef id _Nonnull (^RACReduceBlock)();
+typedef ValueType _Nonnull (^RACGenericReduceBlock)();
+_Pragma("clang diagnostic pop")
+
 /// Returns an empty stream.
 + (__kindof RACStream<ValueType> *)empty;
 
@@ -170,7 +176,7 @@ typedef RACStream * _Nullable (^RACStreamBindBlock)(ValueType _Nullable value, B
 ///               return value must be an object. This argument cannot be nil.
 ///
 /// Returns a new stream of reduced tuple values.
-- (__kindof RACStream *)reduceEach:(id _Nullable (^)())reduceBlock;
+- (__kindof RACStream *)reduceEach:(RACReduceBlock)reduceBlock;
 
 /// Returns a stream consisting of `value`, followed by the values in the
 /// receiver.
@@ -221,7 +227,7 @@ typedef RACStream * _Nullable (^RACStreamBindBlock)(ValueType _Nullable value, B
 ///
 /// Returns a new stream containing the results from each invocation of
 /// `reduceBlock`.
-+ (__kindof RACStream<ValueType> *)zip:(id<NSFastEnumeration>)streams reduce:(id _Nullable (^)())reduceBlock;
++ (__kindof RACStream<ValueType> *)zip:(id<NSFastEnumeration>)streams reduce:(RACGenericReduceBlock)reduceBlock;
 
 /// Returns a stream obtained by concatenating `streams` in order.
 + (__kindof RACStream<ValueType> *)concat:(id<NSFastEnumeration>)streams;
diff --git a/ReactiveObjC/RACStream.m b/ReactiveObjC/RACStream.m
index c362eb847..431b6c6b9 100644
--- a/ReactiveObjC/RACStream.m
+++ b/ReactiveObjC/RACStream.m
@@ -139,7 +139,7 @@ - (__kindof RACStream *)ignore:(id)value {
 	}] setNameWithFormat:@"[%@] -ignore: %@", self.name, RACDescription(value)];
 }
 
-- (__kindof RACStream *)reduceEach:(id (^)())reduceBlock {
+- (__kindof RACStream *)reduceEach:(RACReduceBlock)reduceBlock {
 	NSCParameterAssert(reduceBlock != nil);
 
 	__weak RACStream *stream __attribute__((unused)) = self;
@@ -234,7 +234,7 @@ + (__kindof RACStream *)zip:(id<NSFastEnumeration>)streams {
 	}] setNameWithFormat:@"+zip: %@", streams];
 }
 
-+ (__kindof RACStream *)zip:(id<NSFastEnumeration>)streams reduce:(id (^)())reduceBlock {
++ (__kindof RACStream *)zip:(id<NSFastEnumeration>)streams reduce:(RACGenericReduceBlock)reduceBlock {
 	NSCParameterAssert(reduceBlock != nil);
 
 	RACStream *result = [self zip:streams];
diff --git a/ReactiveObjC/extobjc/EXTScope.h b/ReactiveObjC/extobjc/EXTScope.h
index 4a16f4ae9..8456e8339 100644
--- a/ReactiveObjC/extobjc/EXTScope.h
+++ b/ReactiveObjC/extobjc/EXTScope.h
@@ -88,7 +88,7 @@
     _Pragma("clang diagnostic pop")
 
 /*** implementation details follow ***/
-typedef void (^rac_cleanupBlock_t)();
+typedef void (^rac_cleanupBlock_t)(void);
 
 static inline void rac_executeCleanupBlock (__strong rac_cleanupBlock_t *block) {
     (*block)();