diff --git a/toolkit/mozapps/installer/packager.mk b/toolkit/mozapps/installer/packager.mk
index 3581c64561d..bbf53e3a50c 100644
--- a/toolkit/mozapps/installer/packager.mk
+++ b/toolkit/mozapps/installer/packager.mk
@@ -620,7 +620,7 @@ ifeq ($(OS_ARCH),OS2)
 NSS_DLL_SUFFIX	= .DLL
 SIGN_CMD	= $(MOZILLA_DIR)/toolkit/mozapps/installer/os2/sign.cmd $(DIST)
 else
-SIGN_CMD	= $(RUN_TEST_PROGRAM) $(_ABS_DIST)/bin/shlibsign$(BIN_SUFFIX) -v -i
+SIGN_CMD	= $(strip $(RUN_TEST_PROGRAM) $(_ABS_DIST)/bin/shlibsign$(BIN_SUFFIX) -v -i)
 endif
 endif
 
@@ -748,7 +748,8 @@ endif
 	@cp -av $(DIST)/$(STAGEPATH)$(MOZ_PKG_DIR)$(_BINPATH)/. $(DEPTH)/installer-stage/core
 	@(cd $(DEPTH)/installer-stage/core && $(CREATE_PRECOMPLETE_CMD))
 ifdef MOZ_SIGN_PREPARED_PACKAGE_CMD
-	$(MOZ_SIGN_PREPARED_PACKAGE_CMD) $(DEPTH)/installer-stage
+# The && true is necessary to make sure Pymake spins a shell
+	$(MOZ_SIGN_PREPARED_PACKAGE_CMD) $(DEPTH)/installer-stage && true
 endif
 
 elfhack: