diff --git a/include/NTMakefile b/include/NTMakefile
index b0d35daac..3838c4599 100644
--- a/include/NTMakefile
+++ b/include/NTMakefile
@@ -59,6 +59,7 @@ while(<>) {
 
     if ("$(KRB5)") { print "#define KRB5 1\n"; }
     if ("$(KRB4)") { print "#define KRB4 1\n"; }
+    if ("$(WEAK_CRYPTO)") { print "#define HEIM_WEAK_CRYPTO 1\n"; }
     if ("$(PKINIT)") { print "#define PKINIT 1\n"; }
     if ("$(NO_AFS)") { print "#define NO_AFS 1\n"; }
     if ("$(OPENLDAP)") { print "#define OPENLDAP 1\n"; }
diff --git a/windows/NTMakefile.config b/windows/NTMakefile.config
index 9c6777b55..0d4e08742 100644
--- a/windows/NTMakefile.config
+++ b/windows/NTMakefile.config
@@ -98,3 +98,6 @@ DIR_hdbdir=%{COMMON_APPDATA}/heimdal/hdb
 
 # Enable MSLSA cache backend
 HAVE_MSLSA_CACHE=1
+
+# Enable weak crypto
+WEAK_CRYPTO=1