diff --git a/check_version.go b/check_version.go
index c99cb65..7614680 100644
--- a/check_version.go
+++ b/check_version.go
@@ -38,9 +38,8 @@ func shortCommitHash(hash string) string {
 
 // pkgVersionFromGit determines the actual version to be packaged
 // from the git repository status and user preference.
-// Besides returning the upstream version, the "upstream" struct
-// struct fields u.version, u.commitIsh, u.hasRelease and u.isRelease
-// are also set.
+// Besides returning the upstream version, the "upstream" struct fields
+// u.version, u.commitID, u.commitIsh, u.hasRelease and u.isRelease are also set.
 // `preferredRev` should be empty if there are no user preferences.
 // TODO: also support other VCS
 func pkgVersionFromGit(gitdir string, u *upstream, preferredRev string, forcePrerelease bool) (string, error) {
@@ -129,9 +128,10 @@ func pkgVersionFromGit(gitdir string, u *upstream, preferredRev string, forcePre
 	}
 	fullCommitHash := strings.TrimSpace(string(fullCommitHashBytes))
 	lastCommitHash := shortCommitHash(fullCommitHash)
+	u.commitID = fullCommitHash
 	u.commitIsh = lastCommitHash
 
 	// Snapshot versions are based on the packaging date, not the commit date.
-	u.version = fmt.Sprintf("0+git%s.%s\n%%define commit_id %s", packagingDateString(), lastCommitHash, fullCommitHash)
+	u.version = fmt.Sprintf("0+git%s.%s", packagingDateString(), lastCommitHash)
 	return u.version, nil
 }
diff --git a/pack.go b/pack.go
index d1f9494..b183691 100644
--- a/pack.go
+++ b/pack.go
@@ -38,6 +38,7 @@ type upstream struct {
 	tarPath      string   // path to the downloaded or generated orig tarball tempfile
 	compression  string   // compression method, either "gz" or "xz"
 	version      string   // upstream version number, e.g. 0.0~git20180204.1d24609
+	commitID     string   // full commit hash for commit-pinned snapshot builds
 	tag          string   // Latest upstream tag, if any
 	commitIsh    string   // commit-ish corresponding to upstream version to be packaged
 	remote       string   // git remote, set to short hostname if upstream git history is included
@@ -327,7 +328,7 @@ func moduleUsesRepoSubdir(modulePath, repoURL string) bool {
 // the upstream version maps cleanly to %{commit_id} or %{version}.
 func (u *upstream) sourceRefForSpec() (string, error) {
 	ref := u.tag
-	if strings.Contains(u.version, "commit_id") {
+	if u.commitID != "" {
 		ref = "%{commit_id}"
 	} else if u.isRelease && u.tag == "v"+u.version {
 		ref = "v%{version}"
diff --git a/pkgsite_test.go b/pkgsite_test.go
index 0a75e57..a493cf3 100644
--- a/pkgsite_test.go
+++ b/pkgsite_test.go
@@ -428,8 +428,9 @@ func TestGetPkgsitePackageRetriesAmbiguousPathWithLongestModule(t *testing.T) {
 
 func TestSourceURLForSpecUsesCommitIDMacro(t *testing.T) {
 	u := upstream{
-		repoURL: "https://github.com/example/project",
-		version: "0+git20260522.abcdef\n%define commit_id 0123456789abcdef",
+		repoURL:  "https://github.com/example/project",
+		version:  "0+git20260522.abcdef",
+		commitID: "0123456789abcdef",
 	}
 	got, err := u.sourceURLForSpec("github.com/example/project")
 	if err != nil {
@@ -494,8 +495,9 @@ func TestSourceURLForSpecUsesModuleProxyForRepoSubmodule(t *testing.T) {
 
 func TestSourceURLForSpecRejectsCommitIDForRepoSubmodule(t *testing.T) {
 	u := upstream{
-		repoURL: "https://github.com/charmbracelet/x",
-		version: "0+git20260522.abcdef\n%define commit_id abcdef1234567890",
+		repoURL:  "https://github.com/charmbracelet/x",
+		version:  "0+git20260522.abcdef",
+		commitID: "abcdef1234567890",
 	}
 	_, err := u.sourceURLForSpec("github.com/charmbracelet/x/ansi")
 	if err == nil {
@@ -529,7 +531,7 @@ func TestPkgVersionFromGitUsesPackagingDateAndSevenCharHash(t *testing.T) {
 	}, "commit", "-m", "initial")
 
 	fullHash := strings.TrimSpace(runGit(t, dir, nil, "rev-parse", "HEAD"))
-	want := "0+git20250808." + fullHash[:7] + "\n%define commit_id " + fullHash
+	want := "0+git20250808." + fullHash[:7]
 
 	u := upstream{}
 	got, err := pkgVersionFromGit(dir, &u, "", false)
@@ -539,6 +541,12 @@ func TestPkgVersionFromGitUsesPackagingDateAndSevenCharHash(t *testing.T) {
 	if got != want {
 		t.Fatalf("pkgVersionFromGit() = %q, want %q", got, want)
 	}
+	if strings.Contains(got, "\n") || strings.Contains(got, "commit_id") {
+		t.Fatalf("pkgVersionFromGit() returned metadata in version: %q", got)
+	}
+	if u.commitID != fullHash {
+		t.Fatalf("commitID = %q, want %q", u.commitID, fullHash)
+	}
 	if strings.Contains(got, "19990102") {
 		t.Fatalf("pkgVersionFromGit() used commit date: %q", got)
 	}
diff --git a/spec.go b/spec.go
index 0be5c60..5fb632c 100644
--- a/spec.go
+++ b/spec.go
@@ -122,13 +122,8 @@ func writeSpec(dir, gopkg, openRuyiSrc, openRuyiLib, openRuyiProgram, version st
 	fmt.Fprintf(f, "%%define _name           %s\n", upstreamName)
 	fmt.Fprintf(f, "%%define go_import_path  %s\n", gopkg)
 
-	// If pkgVersionFromGit embedded a commit_id define in u.version, extract and write it here
-	commitRe := regexp.MustCompile(`%define\s+commit_id\s+([0-9a-fA-F]+)`)
-	if m := commitRe.FindStringSubmatch(u.version); m != nil {
-		fmt.Fprintf(f, "%%define commit_id %s\n", m[1])
-		// Remove the embedded %define line from version so it doesn't get written to Version: field
-		version = commitRe.ReplaceAllString(version, "")
-		version = strings.TrimSpace(version)
+	if u.commitID != "" {
+		fmt.Fprintf(f, "%%define commit_id %s\n", u.commitID)
 	}
 	fmt.Fprintf(f, "\n")