diff --git a/Source/Headers/Public/CDRFunctions.h b/Source/Headers/Public/CDRFunctions.h
index ae5fe070..b0e7785b 100644
--- a/Source/Headers/Public/CDRFunctions.h
+++ b/Source/Headers/Public/CDRFunctions.h
@@ -9,13 +9,13 @@ extern "C" {
 
 NSArray *CDRReportersFromEnv(const char*defaultReporterClassName);
 
-int CDRRunSpecs();
-OBJC_EXPORT void CDRInjectIntoXCTestRunner();
+int CDRRunSpecs(void);
+OBJC_EXPORT void CDRInjectIntoXCTestRunner(void);
 int CDRRunSpecsWithCustomExampleReporters(NSArray *reporters);
 NSArray *CDRShuffleItemsInArrayWithSeed(NSArray *sortedItems, unsigned int seed);
-NSArray *CDRReportersToRun();
-NSString *CDRGetTestBundleExtension();
-void CDRSuppressStandardPipesWhileLoadingClasses();
+NSArray *CDRReportersToRun(void);
+NSString *CDRGetTestBundleExtension(void);
+void CDRSuppressStandardPipesWhileLoadingClasses(void);
 
 NS_ASSUME_NONNULL_END
 
diff --git a/Source/Headers/Public/CDRSpec.h b/Source/Headers/Public/CDRSpec.h
index 9f6e007d..41ded83f 100644
--- a/Source/Headers/Public/CDRSpec.h
+++ b/Source/Headers/Public/CDRSpec.h
@@ -37,8 +37,8 @@ CDRExample * fit(NSString *, __nullable CDRSpecBlock);
 
 void fail(NSString *);
 
-void CDREnableSpecValidation();
-void CDRDisableSpecValidation();
+void CDREnableSpecValidation(void);
+void CDRDisableSpecValidation(void);
 
 #ifdef __cplusplus
 }