diff --git a/src/beesh.sh.in b/src/beesh.sh.in
index b7b91c5..744fc64 100644
--- a/src/beesh.sh.in
+++ b/src/beesh.sh.in
@@ -157,6 +157,7 @@ function check_rebuild() {
                       echo "${bf}"
                   done | ${BEESORT} | tail -1)
 
+    test -n "${beefile_max}" || exit 1
     eval $(${BEEVERSION} ${beefile_max})
     print_warning "cp ${beefile} ${PWD}/${PKGFULLNAME}-${PKGFULLVERSION}-$((PKGREVISION + 1)).bee"
 
@@ -191,8 +192,35 @@ function check_repositories() {
     fi
 }
 
+function validate_pkg_complete() {
+    test -n "$PKGNAME" -a -n "$PKGVERSION" -a -n "$PKGREVISION" || return 1
+    return 0
+}
+
+function validate_pkg_complete_from_filename() {
+    test -n "$PKGNAME"  -a "$PKGSUFFIX" = '.bee' || return 1
+    test "$PKGFULLVERSION" = '0' && return 0                # versionless. bla-0
+    test -n "$PKGVERSION" -a -n "$PKGREVISION" && return 0  # with version bla-1.2.3-55
+    return 1
+}
+
+###############################################################################
 function build_in_sourcedir() {
-   B=${S}
+   BUILD_IN_SOURCEDIR=1
+}
+
+function bee_die() {
+    print_error $*
+    exit 1
+}
+
+function bee_version() {
+    test -n "$1" || bee_die "bee_version: missing argument"
+    test "$PKGFULLVERSION"="0" -a -z "$PKGREVISION" || bee_die "bee_version: version is already fixed"
+    local oPKGFULLNAME="$PKGFULLNAME"
+    eval $("${BEE_BINDIR}/beeversion" "$1" 2>/dev/null) || bee_die "bee_version: invalid version string"
+    validate_pkg_complete || bee_die "bee_version: please use the proper package versioning (e.g. package-1.0-0)"
+    test "$PKGFULLNAME" = "$oPKGFULLNAME" || bee_die "bee_version: not allowed to change the package name from $oPKGFULLNAME to $PKGFULLNAME"
 }
 
 function add_sourcesubdir() {
@@ -732,9 +760,8 @@ function save_current_package_variables() {
     oPKGREVISION=${PKGREVISION}
 }
 
-function verify_new_package_variables() {
+function extract_new_package_variables() {
     nPKGFULLNAME="${PKGNAME}${PKGEXTRANAME:+_${PKGEXTRANAME}}"
-
     if [ "${oPKGFULLNAME}" != "${PKGFULLNAME}" ] ; then
         if [ "${oPKGFULLNAME}" != "${nPKGFULLNAME}" ] ; then
             print_error "${BEE##*/}: Changing PKGFULLNAME and one of PKGNAME or PKGEXTRANAME is not supported."
@@ -751,10 +778,6 @@ function verify_new_package_variables() {
 
     nPKGFULLVERSION="${PKGVERSION}${PKGEXTRAVERSION:+_${PKGEXTRAVERSION}}"
     if [ "${oPKGFULLVERSION}" != "${PKGFULLVERSION}" ] ; then
-        if [ "${oPKGFULLVERSION}" != "${nPKGFULLVERSION}" ] ; then
-            print_error "${BEE##*/}: Changing PKGFULLVERSION and one of PKGVERSION or PKGEXTRAVERSION is not supported."
-            exit 1
-        fi
         PKGVERSION=${PKGFULLVERSION//_*}
         if [ "$PKGVERSION" = "$PKGFULLVERSION" ] ; then
             PKGEXTRAVERSION=""
@@ -763,9 +786,7 @@ function verify_new_package_variables() {
         fi
     fi
     PKGFULLVERSION="${PKGVERSION}${PKGEXTRAVERSION:+_${PKGEXTRAVERSION}}"
-}
 
-function extract_new_package_variables() {
     if [ "${PKGNAME}" != "${oPKGNAME}" ] ; then
         # pkgname changed! we allow prefixing 'anything-' to the packagename
         if [ "${PKGNAME}" != "${PKGNAME/-${oPKGNAME}}-${oPKGNAME}" ] ; then
@@ -781,31 +802,15 @@ function extract_new_package_variables() {
         fi
         print_info "${COLOR_YELLOW}PKGEXTRANAME changed from '${oPKGEXTRANAME}' to '${PKGEXTRANAME}'"
     fi
-    if [ "${PKGVERSION}" != "${oPKGVERSION}" ] ; then
-        print_error "${BEE##*/}: Invalid change in PKGVERSION(${PKGVERSION}) detected. Changing PKGVERSION is not supported."
-        exit 1
-    fi
-    if [ "${PKGEXTRAVERSION}" != "${oPKGEXTRAVERSION}" ] ; then
-        if [ ! -z "${oPKGEXTRAVERSION}" -a  "${PKGEXTRAVERSION}" != "${oPKGEXTRAVERSION}_${PKGEXTRAVERSION#${oPKGEXTRAVERSION}_}" ] ; then
-            print_error "${BEE##*/}: Invalid change in PKGEXTRAVERSION(${PKGEXTRAVERSION}) detected. Only appending '_something' is supported."
-            exit 1
-        fi
-        print_info "${COLOR_YELLOW}PKGEXTRAVERSION changed from '${oPKGEXTRAVERSION}' to '${PKGEXTRAVERSION}'"
-    fi
-    if [ "${PKGREVISION}" != "${oPKGREVISION}" ] ; then
-        print_error "${BEE##*/}: Invalid change in PKGREVISION(${PKGREVISION}) detected. Changing PKGREVISION is not supported."
-        exit 1
-    fi
 
     PKGFULLPKG=${PKGFULLNAME}-${PKGFULLVERSION}-${PKGREVISION}
 
     # since PKGARCH is now known reconstruct PKGALLPKG
     : ${PKGALLPKG:=${PKGFULLPKG}.${PKGARCH}}
 
-    eval $("${BEE_BINDIR}/beeversion" "${PKGALLPKG}")
+    eval $("${BEE_BINDIR}/beeversion" "${PKGALLPKG}" 2>/dev/null) 
 }
 
-###############################################################################
 ###############################################################################
 ###############################################################################
 
@@ -961,37 +966,42 @@ PKGNAME=
 PKGVERSION=
 PKGREVISION=
 
-eval $("${BEE_BINDIR}/beeversion" "${BEE}")
+eval $("${BEE_BINDIR}/beeversion" "${BEE}" 2>/dev/null)
 
-if [ -z "${PKGNAME}" -o -z "${PKGVERSION}" -o -z "${PKGREVISION}" ] ; then
-    print_error "${BEE}: please use the proper package versioning (e.g. package-1.0-0)"
-    exit 1
-fi
-
-BEEPKGROOT="${BEE_TMP_BUILDROOT}/${PKGNAME}"
-BEEWORKDIR="${BEEPKGROOT}/${PKGFULLPKG}"
-
-F=${BEEPKGROOT}/files
-S=${BEEWORKDIR}/source
-B=${BEEWORKDIR}/build
-D=${BEEWORKDIR}/image
+validate_pkg_complete_from_filename || \
+    bee_die "filename $BEE is invalid. (valid examples: bla-0.bee bla-1.2.3-55.bee bla_lall_x-1.2.3.4_xxx-0.x86_64.bee)"
 
 ###############################################################################
 
 # clear PKGALLPKG since we can't trust PKGARCH in this state
 PKGALLPKG=
 
+S='S_NOT_YET_DEFINED'
 save_current_package_variables
 
 # source file.bee
 . "${BEE}"
 
+if [ "$B" = 'S_NOT_YET_DEFINED' ] ; then
+    print_warning "${BEE}: setting \$B=\"\$S\" is deprecated. use build_in_sourcedir instead."
+    build_in_sourcedir
+fi
+
 # now set PKGARCH if set or changed by user via ARCH=.. and not given via file.arch.bee
 : ${PKGARCH:=${ARCH}}
 
-verify_new_package_variables
 extract_new_package_variables
 
+validate_pkg_complete || bee_die "if you start from a generic file ( package-0.bee ) you need to call bee_version from inside the bee file (e.g. bee_version package-1.0-0)"
+
+BEEPKGROOT="${BEE_TMP_BUILDROOT}/${PKGNAME}"
+BEEWORKDIR="${BEEPKGROOT}/${PKGFULLPKG}"
+
+F=${BEEPKGROOT}/files
+S=${BEEWORKDIR}/source
+B=${BEEWORKDIR}/build
+D=${BEEWORKDIR}/image
+
 config_handle_deprecated_beefile
 expand_prefix_variables
 config_export
@@ -1053,6 +1063,11 @@ for t in "${bee_buildmagic[@]}" ; do
     fi
 done
 
+if [ "$BUILD_IN_SOURCEDIR" ] ; then
+   print_info "BUILD_IN_SOURCEDIR requested"
+   B="$S"
+fi
+
 bee_init_buildinsourcedir
 
 print_info "changing to build directory: ${B}"