diff --git a/src/book.cpp b/src/book.cpp
index 8a55ec5..0431600 100644
--- a/src/book.cpp
+++ b/src/book.cpp
@@ -21,7 +21,11 @@
 #include "log.hpp"
 #include "zip.hpp"
 
+#include <boost/locale/message.hpp>
 #include <boost/regex.hpp>
+#include <fmt/format.h>
+#include <fmt/ostream.h> // For compatibility with fmt 4.
+#include <pugixml.hpp>
 
 #include <algorithm>
 #include <memory>
@@ -32,6 +36,8 @@
 namespace epubgrep::book
 {
 
+using boost::locale::translate;
+using fmt::format;
 using std::string;
 
 book read(const fs::path filepath, const bool raw)
@@ -42,7 +48,7 @@ book read(const fs::path filepath, const bool raw)
                                        {
                                            if (!raw)
                                            {
-                                               return zip::list_spine(filepath);
+                                               return list_spine(filepath);
                                            }
                                            return zip::list(filepath);
                                        }()};
@@ -183,4 +189,80 @@ string page(const document &doc, const size_t pos)
     return string(last);
 }
 
+std::vector<string> list_spine(const fs::path &filepath)
+{
+    const auto opf_file_path{
+        [&filepath]
+        {
+            pugi::xml_document xml;
+            const std::string container{
+                zip::read_file(filepath, "META-INF/container.xml")};
+            const auto result{xml.load_buffer(&container[0], container.size())};
+            if (result)
+            {
+                return fs::path{xml.child("container")
+                                    .child("rootfiles")
+                                    .first_child()
+                                    .attribute("full-path")
+                                    .value()};
+            }
+            LOG(log::sev::error) << result.description() << '\n';
+
+            return fs::path{};
+        }()};
+
+    std::vector<std::string> spine_filepaths;
+    if (!opf_file_path.empty())
+    {
+        DEBUGLOG << "Parsing " << opf_file_path;
+        pugi::xml_document xml;
+        const std::string opf_file{
+            zip::read_file(filepath, opf_file_path.string())};
+        const auto result{xml.load_buffer(&opf_file[0], opf_file.size())};
+        if (result)
+        {
+            auto manifest{xml.child("package").child("manifest")};
+            if (manifest == nullptr)
+            {
+                manifest = xml.child("opf:package").child("opf:manifest");
+            }
+            auto spine{xml.child("package").child("spine")};
+            if (spine == nullptr)
+            {
+                spine = xml.child("opf:package").child("opf:spine");
+            }
+
+            for (const auto &itemref : spine)
+            {
+                const auto &idref{itemref.attribute("idref").value()};
+                const auto &item{manifest.find_child_by_attribute("id", idref)};
+                auto href{helpers::urldecode(item.attribute("href").value())};
+                if (href[0] != '/')
+                {
+                    href = (opf_file_path.parent_path() /= href);
+                }
+                DEBUGLOG << "Found in spine: " << href;
+                spine_filepaths.emplace_back(href);
+            }
+        }
+        else
+        {
+            LOG(log::sev::error) << "XML: " << result.description() << '\n';
+        }
+    }
+
+    if (opf_file_path.empty() || spine_filepaths.empty())
+    {
+        LOG(log::sev::error)
+            << format(translate("{0:s} is damaged. Could not read spine. "
+                                "Skipping file.\n")
+                          .str()
+                          .data(),
+                      filepath);
+        return {};
+    }
+
+    return spine_filepaths;
+}
+
 } // namespace epubgrep::book
diff --git a/src/book.hpp b/src/book.hpp
index 16071ae..bcd3ff7 100644
--- a/src/book.hpp
+++ b/src/book.hpp
@@ -62,6 +62,9 @@ struct book
 //! Return current page if possible.
 [[nodiscard]] std::string page(const document &doc, size_t pos);
 
+//! Returns the files in the EPUB “spine” (all pages that are actually text).
+[[nodiscard]] std::vector<string> list_spine(const fs::path &filepath);
+
 } // namespace epubgrep::book
 
 #endif // EPUBGREP_BOOK_HPP
diff --git a/src/zip.cpp b/src/zip.cpp
index 1c6f858..6907f8f 100644
--- a/src/zip.cpp
+++ b/src/zip.cpp
@@ -25,7 +25,6 @@
 #include <boost/locale/message.hpp>
 #include <fmt/format.h>
 #include <fmt/ostream.h> // For compatibility with fmt 4.
-#include <pugixml.hpp>
 
 #include <cstdlib>
 #include <cstring>
@@ -165,79 +164,4 @@ void close_file(struct archive *zipfile, const fs::path &filepath)
     }
 }
 
-std::vector<std::string> list_spine(const fs::path &filepath)
-{
-    const auto opf_file_path{
-        [&filepath]
-        {
-            pugi::xml_document xml;
-            const std::string container{
-                read_file(filepath, "META-INF/container.xml")};
-            const auto result{xml.load_buffer(&container[0], container.size())};
-            if (result)
-            {
-                return fs::path{xml.child("container")
-                                    .child("rootfiles")
-                                    .first_child()
-                                    .attribute("full-path")
-                                    .value()};
-            }
-            LOG(log::sev::error) << result.description() << '\n';
-
-            return fs::path{};
-        }()};
-
-    std::vector<std::string> spine_filepaths;
-    if (!opf_file_path.empty())
-    {
-        DEBUGLOG << "Parsing " << opf_file_path;
-        pugi::xml_document xml;
-        const std::string opf_file{read_file(filepath, opf_file_path.string())};
-        const auto result{xml.load_buffer(&opf_file[0], opf_file.size())};
-        if (result)
-        {
-            auto manifest{xml.child("package").child("manifest")};
-            if (manifest == nullptr)
-            {
-                manifest = xml.child("opf:package").child("opf:manifest");
-            }
-            auto spine{xml.child("package").child("spine")};
-            if (spine == nullptr)
-            {
-                spine = xml.child("opf:package").child("opf:spine");
-            }
-
-            for (const auto &itemref : spine)
-            {
-                const auto &idref{itemref.attribute("idref").value()};
-                const auto &item{manifest.find_child_by_attribute("id", idref)};
-                auto href{helpers::urldecode(item.attribute("href").value())};
-                if (href[0] != '/')
-                {
-                    href = (opf_file_path.parent_path() /= href);
-                }
-                DEBUGLOG << "Found in spine: " << href;
-                spine_filepaths.emplace_back(href);
-            }
-        }
-        else
-        {
-            LOG(log::sev::error) << "XML: " << result.description() << '\n';
-        }
-    }
-
-    if (opf_file_path.empty() || spine_filepaths.empty())
-    {
-        LOG(log::sev::error)
-            << format(translate("{0:s} is damaged. Could not read spine. "
-                                "Skipping file.\n")
-                          .str()
-                          .data(),
-                      filepath);
-        return {};
-    }
-
-    return spine_filepaths;
-}
-
 } // namespace epubgrep::zip
diff --git a/src/zip.hpp b/src/zip.hpp
index 05f04b0..e8719a5 100644
--- a/src/zip.hpp
+++ b/src/zip.hpp
@@ -43,9 +43,6 @@ namespace epubgrep::zip
 //! Close zip file.
 void close_file(struct archive *zipfile, const fs::path &filepath);
 
-//! Returns the files in the EPUB “spine” (all pages that are actually text).
-[[nodiscard]] std::vector<std::string> list_spine(const fs::path &filepath);
-
 //! It's std::runtime_error, but with another name.
 class exception : public std::runtime_error
 {