diff --git a/Recipe b/Recipe
index 379f9b6b..952373f2 100644
--- a/Recipe
+++ b/Recipe
@@ -134,6 +134,18 @@
 # ------------------------------------------------------------
 # Additional text added verbatim to each individual Makefile.
 
+!cflags am version -DSOURCE_COMMIT=\"`git rev-parse HEAD 2>/dev/null`\"
+!begin am
+BUILT_SOURCES = empty.h
+CLEANFILES = empty.h
+empty.h: $(allsources)
+	echo '/* Empty file touched by automake makefile to force rebuild of version.o */' >$@
+
+!end
+!begin >empty.h
+/* Empty file touched by automake makefile to force rebuild of version.o */
+!end
+
 !begin vc vars
 CFLAGS = $(CFLAGS) /DHAS_GSSAPI
 !end
diff --git a/version.c b/version.c
index 231c1a75..59e9ca75 100644
--- a/version.c
+++ b/version.c
@@ -8,6 +8,10 @@
  * to do here is to drop it into variables of the right names.
  */
 
+#ifdef SOURCE_COMMIT
+#include "empty.h"
+#endif
+
 #include "version.h"
 
 const char ver[] = TEXTVER;
diff --git a/version.h b/version.h
index a9fab692..26242ad6 100644
--- a/version.h
+++ b/version.h
@@ -11,4 +11,25 @@
 #define TEXTVER "Unidentified build"
 #define SSHVER "PuTTY-Unidentified-Local-Build"
 #define BINARY_VERSION 0,0,0,0
+
+#ifndef SOURCE_COMMIT
+/*
+ * git commit id from which this build was made. This is defined by
+ * Buildscr for official builds - both source archives and prebuilt
+ * binaries - in the course of overwriting this file as described
+ * above. But we put it here under ifdef, so that it can also be
+ * passed in on the command line for Unix local development builds,
+ * which I treat specially because Unix developers - e.g. me - are
+ * quite likely to run 'make install' straight out of their dev
+ * directory so as to use the bleeding-edge code for day-to-day
+ * running.
+ *
+ * Windows doesn't really need the same treatment, because the easiest
+ * way to install a build properly on Windows is to run the installer,
+ * and the easiest way to do that is to run Buildscr, which will
+ * populate this field its own way. It's only the Unix automake build
+ * where you might go straight from local 'make' to 'make install'
+ * without going through Buildscr.
+ */
 #define SOURCE_COMMIT "unavailable"
+#endif