diff --git a/Makefile b/Makefile
index 4345290b..7d5fad9e 100644
--- a/Makefile
+++ b/Makefile
@@ -786,6 +786,7 @@ endif
 	@cp -rp lib/musl/src/exit            build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/include         build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/internal        build/release/tinygo/lib/musl/src
+	@cp -rp lib/musl/src/legacy          build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/malloc          build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/mman            build/release/tinygo/lib/musl/src
 	@cp -rp lib/musl/src/math            build/release/tinygo/lib/musl/src
diff --git a/builder/builtins.go b/builder/builtins.go
index 121398fa..f3581614 100644
--- a/builder/builtins.go
+++ b/builder/builtins.go
@@ -181,11 +181,11 @@ var CompilerRT = Library{
 		// Development build.
 		return filepath.Join(goenv.Get("TINYGOROOT"), "lib/compiler-rt-builtins")
 	},
-	librarySources: func(target string) []string {
+	librarySources: func(target string) ([]string, error) {
 		builtins := append([]string{}, genericBuiltins...) // copy genericBuiltins
 		if strings.HasPrefix(target, "arm") || strings.HasPrefix(target, "thumb") {
 			builtins = append(builtins, aeabiBuiltins...)
 		}
-		return builtins
+		return builtins, nil
 	},
 }
diff --git a/builder/library.go b/builder/library.go
index 385f1610..06b57632 100644
--- a/builder/library.go
+++ b/builder/library.go
@@ -29,7 +29,7 @@ type Library struct {
 	sourceDir func() string
 
 	// The source files, relative to sourceDir.
-	librarySources func(target string) []string
+	librarySources func(target string) ([]string, error)
 
 	// The source code for the crt1.o file, relative to sourceDir.
 	crt1Source string
@@ -219,7 +219,11 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 
 	// Create jobs to compile all sources. These jobs are depended upon by the
 	// archive job above, so must be run first.
-	for _, path := range l.librarySources(target) {
+	paths, err := l.librarySources(target)
+	if err != nil {
+		return nil, nil, err
+	}
+	for _, path := range paths {
 		// Strip leading "../" parts off the path.
 		cleanpath := path
 		for strings.HasPrefix(cleanpath, "../") {
diff --git a/builder/mingw-w64.go b/builder/mingw-w64.go
index 27fefee0..db8b43c3 100644
--- a/builder/mingw-w64.go
+++ b/builder/mingw-w64.go
@@ -31,9 +31,9 @@ var MinGW = Library{
 		// No flags necessary because there are no files to compile.
 		return nil
 	},
-	librarySources: func(target string) []string {
+	librarySources: func(target string) ([]string, error) {
 		// We only use the UCRT DLL file. No source files necessary.
-		return nil
+		return nil, nil
 	},
 }
 
diff --git a/builder/musl.go b/builder/musl.go
index 8d577f66..bdfdc4a8 100644
--- a/builder/musl.go
+++ b/builder/musl.go
@@ -106,7 +106,7 @@ var Musl = Library{
 		}
 	},
 	sourceDir: func() string { return filepath.Join(goenv.Get("TINYGOROOT"), "lib/musl/src") },
-	librarySources: func(target string) []string {
+	librarySources: func(target string) ([]string, error) {
 		arch := compileopts.MuslArchitecture(target)
 		globs := []string{
 			"env/*.c",
@@ -125,11 +125,14 @@ var Musl = Library{
 			"stdio/*.c",
 			"string/*.c",
 			"thread/" + arch + "/*.s",
-			"thread/" + arch + "/*.c",
 			"thread/*.c",
 			"time/*.c",
 			"unistd/*.c",
 		}
+		if arch == "arm" {
+			// These files need to be added to the start for some reason.
+			globs = append([]string{"thread/arm/*.c"}, globs...)
+		}
 
 		var sources []string
 		seenSources := map[string]struct{}{}
@@ -143,13 +146,16 @@ var Musl = Library{
 				// > ErrBadPattern, when pattern is malformed.
 				// So the only possible error is when the (statically defined)
 				// pattern is wrong. In other words, a programming bug.
-				panic("could not glob source dirs: " + err.Error())
+				return nil, fmt.Errorf("musl: could not glob source dirs: %w", err)
+			}
+			if len(matches) == 0 {
+				return nil, fmt.Errorf("musl: did not find any files for pattern %#v", pattern)
 			}
 			for _, match := range matches {
 				relpath, err := filepath.Rel(basepath, match)
 				if err != nil {
 					// Not sure if this is even possible.
-					panic(err)
+					return nil, err
 				}
 				// Make sure architecture specific files override generic files.
 				id := strings.ReplaceAll(relpath, "/"+arch+"/", "/")
@@ -161,7 +167,7 @@ var Musl = Library{
 				sources = append(sources, relpath)
 			}
 		}
-		return sources
+		return sources, nil
 	},
 	crt1Source: "../crt/crt1.c", // lib/musl/crt/crt1.c
 }
diff --git a/builder/picolibc.go b/builder/picolibc.go
index d0786ee3..1251f5ef 100644
--- a/builder/picolibc.go
+++ b/builder/picolibc.go
@@ -38,8 +38,8 @@ var Picolibc = Library{
 		}
 	},
 	sourceDir: func() string { return filepath.Join(goenv.Get("TINYGOROOT"), "lib/picolibc/newlib") },
-	librarySources: func(target string) []string {
-		return picolibcSources
+	librarySources: func(target string) ([]string, error) {
+		return picolibcSources, nil
 	},
 }