diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index 90f43d60f9..3701f15fed 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -166,7 +166,7 @@ DOCTARGETS = $(DOCTARGETS) capi
 ! endif
 !endif
 !ifndef INSTALLDOC
-! if "$(DOCTARGETS)" == ""
+! if "$(DOCTARGETS)" != ""
 INSTALLDOC = all
 ! else
 INSTALLDOC = nodoc