diff --git a/Buildscr b/Buildscr
index 090e89a0..d48f5a48 100644
--- a/Buildscr
+++ b/Buildscr
@@ -5,6 +5,7 @@ module putty
 
 # Set up the arguments for the main make command.
 set Makever -DSVN_REV=$(revision)
+ifneq "$(!numeric $(revision))" "yes" set Makever $(Makever) -DMODIFIED
 ifneq "$(RELEASE)" "" set Makever $(Makever) -DRELEASE=$(RELEASE)
 ifneq "$(date)" "" set Makever $(Makever) -DSNAPSHOT=$(date)
 set Makeargs VER="$(Makever)"
diff --git a/windows/version.rc2 b/windows/version.rc2
index 049dbe53..8474a62b 100644
--- a/windows/version.rc2
+++ b/windows/version.rc2
@@ -50,7 +50,11 @@
 #endif
 
 #define VERSION_TEXT "Development snapshot " STR(SNAPSHOT) ":r" STR(SVN_REV)
+#ifdef MODIFIED
+#define BINARY_VERSION 0,0,0,0
+#else
 #define BINARY_VERSION BASE_VERSION,SVN_REV,0
+#endif
 
 #elif defined RELEASE
 
@@ -60,7 +64,11 @@
 #elif defined SVN_REV
 
 #define VERSION_TEXT "Custom build r" STR(SVN_REV)
+#ifdef MODIFIED
+#define BINARY_VERSION 0,0,0,0
+#else
 #define BINARY_VERSION BASE_VERSION,SVN_REV,0
+#endif
 
 #else