diff --git a/vlib/v/builder/builder.v b/vlib/v/builder/builder.v
index d1124437bb..461b6e5256 100644
--- a/vlib/v/builder/builder.v
+++ b/vlib/v/builder/builder.v
@@ -25,6 +25,7 @@ mut:
 pub mut:
 	module_search_paths []string
 	parsed_files        []ast.File
+	cached_msvc			MsvcResult
 }
 
 pub fn new_builder(pref &pref.Preferences) Builder {
@@ -37,6 +38,12 @@ pub fn new_builder(pref &pref.Preferences) Builder {
 	if pref.use_color == .never {
 		util.emanager.set_support_color(false)
 	}
+	msvc := find_msvc() or {
+		if pref.ccompiler == 'msvc' {
+			verror('Cannot find MSVC on this OS')
+		}
+		MsvcResult { valid: false }
+	}
 	return Builder{
 		pref: pref
 		table: table
@@ -50,6 +57,7 @@ pub fn new_builder(pref &pref.Preferences) Builder {
 		} else {
 			100
 		}
+		cached_msvc: msvc
 	}
 	// max_nr_errors: pref.error_limit ?? 100 TODO potential syntax?
 }
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index 389cc03fc5..3624c2aba6 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -661,7 +661,7 @@ fn (c &Builder) build_thirdparty_obj_files() {
 		if flag.value.ends_with('.o') {
 			rest_of_module_flags := c.get_rest_of_module_cflags(flag)
 			if c.pref.ccompiler == 'msvc' {
-				build_thirdparty_obj_file_with_msvc(flag.value, rest_of_module_flags)
+				c.build_thirdparty_obj_file_with_msvc(flag.value, rest_of_module_flags)
 			} else {
 				c.build_thirdparty_obj_file(flag.value, rest_of_module_flags)
 			}
@@ -684,16 +684,7 @@ fn (mut v Builder) build_thirdparty_obj_file(path string, moduleflags []cflag.CF
 		return
 	}
 	println('$obj_path not found, building it...')
-	parent := os.dir(obj_path)
-	files := os.ls(parent) or {
-		panic(err)
-	}
-	mut cfiles := ''
-	for file in files {
-		if file.ends_with('.c') {
-			cfiles += '"' + os.real_path(parent + os.path_separator + file) + '" '
-		}
-	}
+	cfiles := '${path[..path.len-2]}.c'
 	btarget := moduleflags.c_options_before_target()
 	atarget := moduleflags.c_options_after_target()
 	cppoptions := if v.pref.ccompiler.contains('++') { ' -fpermissive -w ' } else { '' }
diff --git a/vlib/v/builder/msvc.v b/vlib/v/builder/msvc.v
index 67418c800c..4b0d38d65a 100644
--- a/vlib/v/builder/msvc.v
+++ b/vlib/v/builder/msvc.v
@@ -18,6 +18,7 @@ struct MsvcResult {
 	ucrt_include_path   string
 	vs_include_path     string
 	shared_include_path string
+	valid				bool
 }
 
 // shell32 for RegOpenKeyExW etc
@@ -183,15 +184,16 @@ fn find_msvc() ?MsvcResult {
 			ucrt_include_path: wk.ucrt_include_path
 			vs_include_path: vs.include_path
 			shared_include_path: wk.shared_include_path
+			valid: true
 		}
 	} $else {
-		verror('Cannot find msvc on this OS')
 		return error('msvc not found')
 	}
 }
 
 pub fn (mut v Builder) cc_msvc() {
-	r := find_msvc() or {
+	r := v.cached_msvc
+	if r.valid == false {
 		verror('Cannot find MSVC on this OS')
 		return
 	}
@@ -309,36 +311,30 @@ pub fn (mut v Builder) cc_msvc() {
 	os.rm(out_name_obj)
 }
 
-fn build_thirdparty_obj_file_with_msvc(path string, moduleflags []cflag.CFlag) {
-	msvc := find_msvc() or {
-		println('Could not find visual studio')
+fn (mut v Builder) build_thirdparty_obj_file_with_msvc(path string, moduleflags []cflag.CFlag) {
+	msvc := v.cached_msvc
+	
+	if msvc.valid == false {
+		verror('Cannot find MSVC on this OS')
 		return
 	}
 	// msvc expects .obj not .o
 	mut obj_path := '${path}bj'
 	obj_path = os.real_path(obj_path)
 	if os.exists(obj_path) {
-		println('$obj_path already built.')
+		// println('$obj_path already built.')
 		return
 	}
 	println('$obj_path not found, building it (with msvc)...')
-	parent := os.dir(obj_path)
-	files := os.ls(parent) or {
-		panic(err)
-	}
-	mut cfiles := ''
-	for file in files {
-		if file.ends_with('.c') {
-			cfiles += '"' + os.real_path(parent + os.path_separator + file) + '" '
-		}
-	}
-	include_string := '-I "$msvc.ucrt_include_path" -I "$msvc.vs_include_path" -I "$msvc.um_include_path" -I "$msvc.shared_include_path"'
+	cfiles := '${path[..path.len-2]}.c'
+	flags := msvc_string_flags(moduleflags)
+	inc_dirs := flags.inc_paths.join(' ')
+	defines := flags.defines.join(' ')
+	include_string := '-I "$msvc.ucrt_include_path" -I "$msvc.vs_include_path" -I "$msvc.um_include_path" -I "$msvc.shared_include_path" $inc_dirs'
 	// println('cfiles: $cfiles')
-	btarget := moduleflags.c_options_before_target_msvc()
-	atarget := moduleflags.c_options_after_target_msvc()
-	cmd := '"$msvc.full_cl_exe_path" /volatile:ms /DNDEBUG $include_string /c $btarget $cfiles $atarget /Fo"$obj_path"'
+	cmd := '"$msvc.full_cl_exe_path" /volatile:ms /DNDEBUG $defines $include_string /c $cfiles /Fo"$obj_path"'
 	// NB: the quotes above ARE balanced.
-	println('thirdparty cmd line: $cmd')
+	// println('thirdparty cmd line: $cmd')
 	res := os.exec(cmd) or {
 		println('msvc: failed thirdparty object build cmd: $cmd')
 		verror(err)
@@ -357,6 +353,7 @@ mut:
 	real_libs   []string
 	inc_paths   []string
 	lib_paths   []string
+	defines     []string
 	other_flags []string
 }
 
@@ -365,6 +362,7 @@ pub fn msvc_string_flags(cflags []cflag.CFlag) MsvcStringFlags {
 	mut real_libs := []string{}
 	mut inc_paths := []string{}
 	mut lib_paths := []string{}
+	mut defines := []string{}
 	mut other_flags := []string{}
 	for flag in cflags {
 		// println('fl: $flag.name | flag arg: $flag.value')
@@ -392,6 +390,8 @@ pub fn msvc_string_flags(cflags []cflag.CFlag) MsvcStringFlags {
 		} else if flag.value.ends_with('.o') {
 			// msvc expects .obj not .o
 			other_flags << '"${flag.value}bj"'
+		} else if flag.value.starts_with('-D') {
+			defines << '/D${flag.value[2..]}'
 		} else {
 			other_flags << flag.value
 		}
@@ -404,6 +404,7 @@ pub fn msvc_string_flags(cflags []cflag.CFlag) MsvcStringFlags {
 		real_libs: real_libs
 		inc_paths: inc_paths
 		lib_paths: lpaths
+		defines: defines
 		other_flags: other_flags
 	}
 }
diff --git a/vlib/v/cflag/cflags.v b/vlib/v/cflag/cflags.v
index 9af675670c..99c0389591 100644
--- a/vlib/v/cflag/cflags.v
+++ b/vlib/v/cflag/cflags.v
@@ -44,7 +44,7 @@ pub fn (cflags []CFlag) c_options_before_target() string {
 	// -I flags, optimization flags and so on
 	mut args := []string{}
 	for flag in cflags {
-		if flag.name != '-l' {
+		if flag.name != '-l' && !flag.value.ends_with('.o') {
 			args << flag.format()
 		}
 	}