diff --git a/Makefile b/Makefile
index 0799898e0b..613f2ce8f5 100644
--- a/Makefile
+++ b/Makefile
@@ -551,9 +551,15 @@ TGZ_MODE =
 # (or archive) only in source form:
 PKG_SOURCE_MODE = 
 
-# Set a base64-encoded list of strings for an executable and argument
-# to run on an installer (on the client machine) before the installer
-# is uploaded, or empty for no post-process action:
+# Set to a base64-encoded list of strings for an executable and
+# arguments to run on an assembled directory (on the client machine)
+# before it is packaged into an installer, or empty for no pre-process
+# action:
+INSTALLER_PRE_PROCESS_BASE64 =
+
+# Set to a base64-encoded list of strings for an executable and
+# arguments to run on an installer (on the client machine) before the
+# installer is uploaded, or empty for no post-process action:
 INSTALLER_POST_PROCESS_BASE64 =
 
 # Human-readable name (spaces allowed), installation name base, and
@@ -811,6 +817,7 @@ PROP_ARGS = SERVER=$(SERVER) SERVER_PORT=$(SERVER_PORT) SERVER_HOSTS="$(SERVER_H
             DIST_DESC="$(DIST_DESC)" README="$(README)" SIGN_IDENTITY="$(SIGN_IDENTITY)" \
             OSSLSIGNCODE_ARGS_BASE64="$(OSSLSIGNCODE_ARGS_BASE64)" JOB_OPTIONS="$(JOB_OPTIONS)" \
             TGZ_MODE=$(TGZ_MODE) TEST_PKGS="$(TEST_PKGS)" \
+            INSTALLER_PRE_PROCESS_BASE64="$(INSTALLER_PRE_PROCESS_BASE64)" \
             INSTALLER_POST_PROCESS_BASE64="$(INSTALLER_POST_PROCESS_BASE64)"
 
 COPY_ARGS = $(PROP_ARGS) \
@@ -877,7 +884,9 @@ bundle-cross-from-server:
 
 UPLOAD_q = --readme "$(README)" --upload "$(UPLOAD)" --desc "$(DIST_DESC)"
 DIST_ARGS_q = $(UPLOAD_q) $(RELEASE_MODE) $(SOURCE_MODE) $(VERSIONLESS_MODE) \
-              $(MAC_PKG_MODE) $(TGZ_MODE) --post-process "$(INSTALLER_POST_PROCESS_BASE64)" \
+              $(MAC_PKG_MODE) $(TGZ_MODE) \
+              --pre-process "$(INSTALLER_PRE_PROCESS_BASE64)" \
+              --post-process "$(INSTALLER_POST_PROCESS_BASE64)" \
               "$(DIST_NAME)" $(DIST_BASE) $(DIST_DIR) "$(DIST_SUFFIX)" \
               "$(SIGN_IDENTITY)" "$(OSSLSIGNCODE_ARGS_BASE64)"