diff --git a/BugsnagNetworkRequestPlugin/BugsnagNetworkRequestPlugin/NSURLSession+Tracing.m b/BugsnagNetworkRequestPlugin/BugsnagNetworkRequestPlugin/NSURLSession+Tracing.m
index a60f9be80..e0b8d0444 100644
--- a/BugsnagNetworkRequestPlugin/BugsnagNetworkRequestPlugin/NSURLSession+Tracing.m
+++ b/BugsnagNetworkRequestPlugin/BugsnagNetworkRequestPlugin/NSURLSession+Tracing.m
@@ -21,7 +21,7 @@ static IMP set_class_imp(Class _Nonnull class, SEL selector, id _Nonnull impleme
     }
 }
 
-static void replace_NSURLSession_sessionWithConfigurationDelegateQueue() {
+static void replace_NSURLSession_sessionWithConfigurationDelegateQueue(void) {
     Class class = NSURLSession.class;
     SEL selector = @selector(sessionWithConfiguration:delegate:delegateQueue:);
     typedef NSURLSession *(*IMPPrototype)(id, SEL, NSURLSessionConfiguration *,
@@ -42,7 +42,7 @@ static void replace_NSURLSession_sessionWithConfigurationDelegateQueue() {
     });
 }
 
-static void replace_NSURLSession_sharedSession() {
+static void replace_NSURLSession_sharedSession(void) {
     set_class_imp(NSURLSession.class, @selector(sharedSession), ^(__unused id self) {
         static NSURLSession *session;
         static dispatch_once_t onceToken;
@@ -60,7 +60,7 @@ static void replace_NSURLSession_sharedSession() {
     });
 }
 
-void bsg_installNSURLSessionTracing() {
+void bsg_installNSURLSessionTracing(void) {
     replace_NSURLSession_sessionWithConfigurationDelegateQueue();
     replace_NSURLSession_sharedSession();
 }
diff --git a/Tests/BugsnagTests/BugsnagTests.m b/Tests/BugsnagTests/BugsnagTests.m
index f7c80bc27..268f76665 100644
--- a/Tests/BugsnagTests/BugsnagTests.m
+++ b/Tests/BugsnagTests/BugsnagTests.m
@@ -49,6 +49,7 @@ - (void)testBugsnagMetadataAddition {
         
         // Add some additional metadata once we're sure it's not already there
         [client addMetadata:@"aValue2" withKey:@"aKey2" toSection:@"mySection2"];
+        return NO;
     }];
     
     [client notify:exception2 block:^BOOL(BugsnagEvent * _Nonnull event) {
@@ -56,6 +57,7 @@ - (void)testBugsnagMetadataAddition {
         XCTAssertEqualObjects([event getMetadataFromSection:@"mySection2" withKey:@"aKey2"], @"aValue2");
         XCTAssertEqual(event.errors[0].errorClass, @"exception2");
         XCTAssertEqual(event.errors[0].errorMessage, @"reason2");
+        return NO;
     }];
 
     // Check nil value causes deletions
@@ -66,6 +68,7 @@ - (void)testBugsnagMetadataAddition {
     [client notify:exception1 block:^BOOL(BugsnagEvent * _Nonnull event) {
         XCTAssertNil([event getMetadataFromSection:@"mySection1" withKey:@"aKey1"]);
         XCTAssertNil([event getMetadataFromSection:@"mySection2" withKey:@"aKey2"]);
+        return NO;
     }];
     
     // Check that event-level metadata alteration doesn't affect configuration-level metadata
@@ -85,6 +88,7 @@ - (void)testBugsnagMetadataAddition {
         
         
         [expectation fulfill];
+        return NO;
     }];
 
     [self waitForExpectationsWithTimeout:0.1 handler:^(NSError * _Nullable error) {
diff --git a/features/fixtures/shared/scenarios/HandledInternalNotifyScenario.swift b/features/fixtures/shared/scenarios/HandledInternalNotifyScenario.swift
index a086b4e71..473ff4308 100644
--- a/features/fixtures/shared/scenarios/HandledInternalNotifyScenario.swift
+++ b/features/fixtures/shared/scenarios/HandledInternalNotifyScenario.swift
@@ -9,7 +9,7 @@ import Foundation
                                     userInfo: nil);
 
         Bugsnag.notify(exception) { (event) -> Bool in
-            let frames = [
+            let frames: [[String: Any]] = [
                 ["method":"foo()", "file":"src/Giraffe.mm", "lineNumber": 200],
                 ["method":"bar()", "file":"parser.js"],
                 ["method":"yes()"]
diff --git a/features/fixtures/shared/scenarios/MetadataRedactionNestedScenario.swift b/features/fixtures/shared/scenarios/MetadataRedactionNestedScenario.swift
index 714aa6451..d39da1a7a 100644
--- a/features/fixtures/shared/scenarios/MetadataRedactionNestedScenario.swift
+++ b/features/fixtures/shared/scenarios/MetadataRedactionNestedScenario.swift
@@ -20,7 +20,7 @@ class MetadataRedactionNestedScenario: Scenario {
     }
 
     override func run() {
-        let dictionary = [
+        let dictionary: [String: [String: Any]] = [
             "alpha": [
                 "password": "foo",
                 "name": "Bob"
@@ -32,7 +32,7 @@ class MetadataRedactionNestedScenario: Scenario {
                     "name": [
                         "title": "Mr"
                     ]
-                ]
+                ] as [String: Any]
             ]
         ]
         Bugsnag.addOnSession { (block) -> Bool in
diff --git a/features/fixtures/shared/scenarios/UnhandledInternalNotifyScenario.swift b/features/fixtures/shared/scenarios/UnhandledInternalNotifyScenario.swift
index e0a479aa3..707afd399 100644
--- a/features/fixtures/shared/scenarios/UnhandledInternalNotifyScenario.swift
+++ b/features/fixtures/shared/scenarios/UnhandledInternalNotifyScenario.swift
@@ -9,7 +9,7 @@ import Foundation
                                     userInfo: nil);
 
         Bugsnag.notify(exception) { (event) -> Bool in
-            let frames = [
+            let frames: [[String: Any]] = [
                 ["method":"bar()", "file":"foo.js", "lineNumber": 43],
                 ["method":"baz()", "file":"[native code]"],
                 ["method":"is_done()"]
diff --git a/features/fixtures/shared/scenarios/spin_malloc.h b/features/fixtures/shared/scenarios/spin_malloc.h
index 96dae0566..2217ee398 100644
--- a/features/fixtures/shared/scenarios/spin_malloc.h
+++ b/features/fixtures/shared/scenarios/spin_malloc.h
@@ -20,7 +20,7 @@ static void * spin_malloc(struct _malloc_zone_t *zone, size_t size) {
 }
 
 // Override malloc() with a version that deadlocks the current thread.
-static inline void install_spin_malloc() {
+static inline void install_spin_malloc(void) {
     malloc_zone_t *zone = malloc_default_zone();
     vm_protect(mach_task_self(), (uintptr_t)zone, sizeof(malloc_zone_t), 0, VM_PROT_READ | VM_PROT_WRITE);
     zone->malloc = spin_malloc;