diff --git a/build/bin/sage-spkg b/build/bin/sage-spkg
index 39621393586..7e8406bc620 100755
--- a/build/bin/sage-spkg
+++ b/build/bin/sage-spkg
@@ -270,13 +270,13 @@ PKG_BASE=`echo "$PKG_NAME" | sed 's/-.*//'` # strip version number
 # in upstream.
 PKG_VER="${PKG_NAME#${PKG_BASE}}"
 PKG_VER="${PKG_VER#-}"
-if [ -n "$PKG_VER" ]; then
-    echo >&2 "Error: Selecting a different version of a package is no longer supported"
-    exit 1
-fi
 PKG_SCRIPTS="$SAGE_ROOT/build/pkgs/$PKG_BASE"
 LOCAL_PKG_VER=`cat $PKG_SCRIPTS/package-version.txt 2>/dev/null`
 PKG_VER="$LOCAL_PKG_VER"
+if [ -n "$PKG_VER" -a "$PKG_VER" != "$LOCAL_PKG_VER" ]; then
+    echo >&2 "Error: Selecting a different version of a package is no longer supported"
+    exit 1
+fi
 if [ -z "$PKG_VER" ]; then
     PKG_NAME="${PKG_BASE}"
 else
@@ -330,15 +330,15 @@ if [ -n "$PKG_NAME_UPSTREAM" ]; then
         error_msg "Error downloading $PKG_NAME_UPSTREAM"
         exit 1
     fi
-fi
-PKG_SRC="$SAGE_DISTFILES/$PKG_NAME_UPSTREAM"
+    PKG_SRC="$SAGE_DISTFILES/$PKG_NAME_UPSTREAM"
 
-# Do a final check that PKG_SRC is a file with an absolute path
-cd /
-if [ ! -d "$PKG_SRC" ]; then
-    echo >&2 "Error: spkg directory '$PKG_SRC' not found."
-    echo >&2 "This shouldn't happen, it is a bug in the sage-spkg script."
-    exit 1
+    # Do a final check that PKG_SRC is a file with an absolute path
+    cd /
+    if [ ! -f "$PKG_SRC" ]; then
+        echo >&2 "Error: spkg file '$PKG_SRC' not found."
+        echo >&2 "This shouldn't happen, it is a bug in the sage-spkg script."
+        exit 1
+    fi
 fi
 
 # Go back to SAGE_ROOT where we have less chance of completely messing
@@ -416,7 +416,7 @@ fi
 # Normal packages: Extract the package
 ##################################################################
 
-if [ -f "$PKG_SCRIPTS"/checksums.ini ]; then
+if [ -n "$PKG_NAME_UPSTREAM" ]; then
     # Normal package
     echo "Setting up build directory for $PKG_NAME"
     cp -RLp "$PKG_SCRIPTS" "$PKG_NAME"
@@ -537,7 +537,8 @@ echo "****************************************************"
 # Poison the proxy variable to forbid downloads in spkg-install
 # for normal packages
 ##################################################################
-if [ -f checksums.ini ]; then
+if [ -n "$PKG_NAME_UPSTREAM" ]; then
+    # Normal package
     export http_proxy=http://192.0.2.0:5187/
     export https_proxy=$http_proxy
     export ftp_proxy=$http_proxy