diff --git a/scripts/build-defaults.shi b/scripts/build-defaults.shi
index 384cce2..570ce89 100644
--- a/scripts/build-defaults.shi
+++ b/scripts/build-defaults.shi
@@ -33,12 +33,12 @@
 # Out: package version (e.g. "1.2.8")
 get_source_package_version () {
     echo "$SOURCE_PACKAGES" | tr ' ' '\n' | \
-        grep -e "^$1" | sed -e "s|^$1-\(.*\)\.tar\..z$|\\1|g"
+        grep -e "^$1-" | sed -e "s|^$1-\(.*\)\.tar\..z$|\\1|g"
 }
 
 # Extract the package name for a given library.
 # $1: Unversioned and unsuffixed package name (e.g. "zlib")
 # Out: package name (e.g. "zlib-1.2.8.tar.gz")
 get_source_package_name () {
-    echo "$SOURCE_PACKAGES" | tr ' ' '\n' | grep -e "^$1"
+    echo "$SOURCE_PACKAGES" | tr ' ' '\n' | grep -e "^$1-"
 }