diff --git a/ChangeLog b/ChangeLog
index ef603de95..6de85588a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,10 @@
 
 Release 1.9.0 (unreleased):
 
+    - svn checkouts now use peg revisions instead of operative revisions,
+      so they'll continue to work if a repository gets reorganized
+      (#20777, ryandesign)
+
     - Use CommonCrypto/CommonDigest instead of OpenSSL libcrypto. (toby)
 
     - Add SHA256 checksums in addition to MD5, SHA1 and RIPEMD160. (afb)
diff --git a/src/port1.0/portfetch.tcl b/src/port1.0/portfetch.tcl
index 566a3500c..3f2052661 100644
--- a/src/port1.0/portfetch.tcl
+++ b/src/port1.0/portfetch.tcl
@@ -533,11 +533,15 @@ proc portfetch::cvsfetch {args} {
 
 # Perform an svn fetch
 proc portfetch::svnfetch {args} {
-    global svn.args svn.revision svn.method
+    global svn.args svn.method svn.revision svn.url
+
+    if {[regexp {\s} ${svn.url}]} {
+        return -code error [msgcat::mc "Subversion URL cannot contain whitespace"]
+    }
 
     set svn.args "${svn.method} ${svn.args}"
     if {[string length ${svn.revision}]} {
-        set svn.args "${svn.args} -r ${svn.revision}"
+        append svn.url "@${svn.revision}"
     }
 
     if {[catch {command_exec svn "" "2>&1"} result]} {