diff --git a/kiss-new b/kiss-new
index 69ba4c2..1fe6de0 100755
--- a/kiss-new
+++ b/kiss-new
@@ -151,8 +151,30 @@ pkg_sources() {
 }
 
 pkg_build() {
-    # Build packages.
-    :
+    # Build packages and turn them into packaged tarballs. This function
+    # also checks checksums, downloads sources and ensure all dependencies
+    # are installed.
+
+    for pkg; do
+        # Find the package's repository files. This needs to keep
+        # happening as we can't store this data in any kind of data
+        # structure.
+        repo_dir=$(pkg_search "$pkg")
+
+        # Ensure that checksums exist prior to building the package.
+        [ -f "$repo_dir/checksums" ] || {
+            log "[$pkg]: Checksums are missing."
+
+            # Instead of dying above, log it to the terminal. Also define a
+            # variable so we *can* die after all checksum files have been
+            # checked.
+            no_checkums="$no_checkums$pkg "
+        }
+    done
+
+    # Die here as packages without checksums were found above.
+    [ "$no_checkums" ] &&
+        die "Run '$kiss checksum ${no_checkums% }' to generate checksums."
 }
 
 pkg_checksums() {