diff --git a/src/Flare.cc b/src/Flare.cc
index 0ab45b7452..99ac2d6ede 100644
--- a/src/Flare.cc
+++ b/src/Flare.cc
@@ -8,7 +8,7 @@
 
 #include "zeek/Reporter.h"
 
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 
 #include <winsock2.h>
 
@@ -31,10 +31,8 @@ namespace zeek::detail
 	{
 
 Flare::Flare()
-#if ! defined(_MSC_VER)
-	: pipe(FD_CLOEXEC, FD_CLOEXEC, O_NONBLOCK, O_NONBLOCK)
-	{
-	}
+#ifndef _MSC_VER
+	: pipe(FD_CLOEXEC, FD_CLOEXEC, O_NONBLOCK, O_NONBLOCK){}
 #else
 	{
 	WSADATA wsaData;
@@ -64,7 +62,7 @@ Flare::Flare()
 	}
 #endif
 
-[[noreturn]] static void bad_pipe_op(const char* which, bool signal_safe)
+	  [[noreturn]] static void bad_pipe_op(const char* which, bool signal_safe)
 	{
 	if ( signal_safe )
 		abort();
@@ -87,7 +85,7 @@ void Flare::Fire(bool signal_safe)
 
 	for ( ;; )
 		{
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 		int n = write(pipe.WriteFD(), &tmp, 1);
 
 #else
@@ -99,7 +97,7 @@ void Flare::Fire(bool signal_safe)
 
 		if ( n < 0 )
 			{
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 			errno = WSAGetLastError();
 			bad_pipe_op("send", signal_safe);
 #endif
@@ -125,7 +123,7 @@ int Flare::Extinguish(bool signal_safe)
 
 	for ( ;; )
 		{
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 		int n = read(pipe.ReadFD(), &tmp, sizeof(tmp));
 #else
 		int n = recv(recvfd, tmp, sizeof(tmp), 0);
@@ -136,7 +134,7 @@ int Flare::Extinguish(bool signal_safe)
 			// Pipe may not be empty yet: try again.
 			continue;
 			}
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 		if ( WSAGetLastError() == WSAEWOULDBLOCK )
 			break;
 		errno = WSAGetLastError();
diff --git a/src/Flare.h b/src/Flare.h
index 6ded8af25e..affae42dfd 100644
--- a/src/Flare.h
+++ b/src/Flare.h
@@ -2,7 +2,7 @@
 
 #pragma once
 
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 #include "Pipe.h"
 #endif
 
@@ -25,7 +25,7 @@ public:
 	 *         Fire()'d and not yet Extinguished()'d.
 	 */
 	int FD() const
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 		{
 		return pipe.ReadFD();
 		}
@@ -52,7 +52,7 @@ public:
 	int Extinguish(bool signal_safe = false);
 
 private:
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 	Pipe pipe;
 #else
 	int sendfd, recvfd;
diff --git a/src/main.cc b/src/main.cc
index 2796ebf1ad..1de09fc9e7 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -9,13 +9,13 @@
 #include "zeek/supervisor/Supervisor.h"
 #include "zeek/zeek-setup.h"
 
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 #include <fcntl.h> // For _O_BINARY.
 #endif
 
 int main(int argc, char** argv)
 	{
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 	_setmode(_fileno(stdout), _O_BINARY);
 	_setmode(_fileno(stderr), _O_BINARY);
 #endif
diff --git a/src/plugin/Manager.cc b/src/plugin/Manager.cc
index 7828af3656..a535d0f43e 100644
--- a/src/plugin/Manager.cc
+++ b/src/plugin/Manager.cc
@@ -3,7 +3,7 @@
 #include "zeek/plugin/Manager.h"
 
 #include <dirent.h>
-#if ! defined(_MSC_VER)
+#ifndef _MSC_VER
 #include <dlfcn.h>
 #include <glob.h>
 #endif
@@ -163,7 +163,7 @@ bool Manager::ActivateDynamicPluginInternal(const std::string& name, bool ok_if_
                                             std::vector<std::string>* errors)
 	{
 // Loading dynamic plugins is not currently supported on Windows platform.
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 	return false;
 #else
 	errors->clear(); // caller should pass it in empty, but just to be sure
diff --git a/src/plugin/Plugin.h b/src/plugin/Plugin.h
index 333df81538..415bc867ae 100644
--- a/src/plugin/Plugin.h
+++ b/src/plugin/Plugin.h
@@ -25,7 +25,7 @@ struct Field;
 namespace zeek
 	{
 
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 #undef VOID
 #endif
 
diff --git a/src/util.cc b/src/util.cc
index bc85bb166e..ca17648fc1 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -2539,7 +2539,7 @@ static void strerror_r_helper(int result, char* buf, size_t buflen)
 
 void zeek_strerror_r(int zeek_errno, char* buf, size_t buflen)
 	{
-#if defined(_MSC_VER)
+#ifdef _MSC_VER
 	auto str = "Error number: " + std::to_string(zeek_errno);
 	auto res = str.data();
 #else