diff --git a/tools/binpac/lib/binpac.h.in b/tools/binpac/lib/binpac.h.in
index b106df9f09..59dab550c3 100644
--- a/tools/binpac/lib/binpac.h.in
+++ b/tools/binpac/lib/binpac.h.in
@@ -3,7 +3,9 @@
 #ifndef binpac_h
 #define binpac_h
 
+#ifndef _MSC_VER
 #include <sys/param.h>
+#endif
 
 #cmakedefine HOST_BIGENDIAN
 #ifdef HOST_BIGENDIAN
@@ -136,7 +138,7 @@ inline string strfmt(const char* format, ...)
 
 } // anonymous namespace
 
-#define binpac_fmt(x...) strfmt(x).c_str()
+#define binpac_fmt(...) strfmt(__VA_ARGS__).c_str()
 
 class RefCount
 {
diff --git a/tools/binpac/lib/binpac_regex.cc b/tools/binpac/lib/binpac_regex.cc
index 9d6b890de4..22edffddcc 100644
--- a/tools/binpac/lib/binpac_regex.cc
+++ b/tools/binpac/lib/binpac_regex.cc
@@ -1,11 +1,11 @@
 
 #include <vector>
 
-class RE_Matcher;
+namespace zeek { class RE_Matcher; }
 
 namespace binpac
 	{
 
-std::vector<RE_Matcher*>* uncompiled_re_matchers = 0;
+std::vector<zeek::RE_Matcher*>* uncompiled_re_matchers = 0;
 
 	}
diff --git a/tools/binpac/src/CMakeLists.txt b/tools/binpac/src/CMakeLists.txt
index 54ceb335c8..f239f64a9b 100644
--- a/tools/binpac/src/CMakeLists.txt
+++ b/tools/binpac/src/CMakeLists.txt
@@ -4,8 +4,13 @@ bison_target(PACParser pac_parse.yy ${BinPAC_BINARY_DIR}/src/pac_parse.cc
              COMPILE_FLAGS "--debug")
 flex_target(PACScanner pac_scan.ll ${BinPAC_BINARY_DIR}/pac_scan.cc)
 add_flex_bison_dependency(PACScanner PACParser)
-set_property(SOURCE pac_scan.cc APPEND_STRING PROPERTY COMPILE_FLAGS "-Wno-sign-compare")
-
+if (MSVC)
+    set_property(SOURCE pac_scan.cc APPEND_STRING PROPERTY COMPILE_FLAGS "/wd4018")
+else()
+    set_property(SOURCE pac_scan.cc APPEND_STRING PROPERTY COMPILE_FLAGS "-Wno-sign-compare")
+endif()
+include(RequireCXX17)
+    
 include_directories(${PROJECT_SOURCE_DIR}/src
                     ${PROJECT_BINARY_DIR}/src)
 
@@ -100,6 +105,10 @@ set(binpac_SRCS
 
 add_executable(binpac ${binpac_SRCS})
 
+if ( MSVC )
+    target_link_libraries(binpac PRIVATE zeek_windows)
+endif()
+
 install(TARGETS binpac DESTINATION bin)
 
 # This is set to assist superprojects that want to build BinPac
diff --git a/tools/binpac/src/pac_dbg.h b/tools/binpac/src/pac_dbg.h
index aebfda38fa..249a882a5c 100644
--- a/tools/binpac/src/pac_dbg.h
+++ b/tools/binpac/src/pac_dbg.h
@@ -6,9 +6,7 @@
 
 extern bool FLAGS_pac_debug;
 
-#define ASSERT(x) assert(x)
-#define DEBUG_MSG(x...)                                                                            \
-	if ( FLAGS_pac_debug )                                                                         \
-	fprintf(stderr, x)
+#define ASSERT(x)	assert(x)
+#define DEBUG_MSG(...)	if ( FLAGS_pac_debug ) fprintf(stderr, __VA_ARGS__)
 
 #endif /* pac_dbg_h */
diff --git a/tools/binpac/src/pac_scan.ll b/tools/binpac/src/pac_scan.ll
index 7917fa98a1..dd90792bff 100644
--- a/tools/binpac/src/pac_scan.ll
+++ b/tools/binpac/src/pac_scan.ll
@@ -20,8 +20,10 @@
 #include "pac_record.h"
 #include "pac_type.h"
 #include "pac_utils.h"
-#include <libgen.h>
+
 #include <errno.h>
+#include <filesystem>
+#include <string_view>
 
 int line_number = 1;
 
@@ -42,6 +44,11 @@ int char_token(int tok)
 
 void include_file(const char *filename);
 
+string dirname(std::string_view path)
+{
+  return std::filesystem::path(path).parent_path().string();
+}
+
 %}
 
 /* EC -- embedded code state */
@@ -334,10 +341,10 @@ void include_file(const char *filename)
         {
         char* tmp = new char[strlen(input_filename.c_str()) + 1];
         strcpy(tmp, input_filename.c_str());
-        char* dir = dirname(tmp);
+        string dir = dirname(tmp);
 
-        if ( dir )
-            full_filename = string(dir) + "/" + filename;
+        if ( ! dir.empty() )
+            full_filename = dir + "/" + filename;
         else
             {
             fprintf(stderr, "%s:%d error: cannot include file \"%s\": %s\n",