diff --git a/lib/asn1/gen.c b/lib/asn1/gen.c
index e3da98e5c..849e38c09 100644
--- a/lib/asn1/gen.c
+++ b/lib/asn1/gen.c
@@ -191,6 +191,7 @@ init_generate (const char *filename, const char *base)
     fprintf (headerfile,
 	     "#include <stddef.h>\n"
 	     "#include <stdint.h>\n"
+	     "#include <errno.h>\n"
 	     "#include <time.h>\n\n");
     fprintf (headerfile,
 	     "#ifndef __asn1_common_definitions__\n"
diff --git a/lib/asn1/template.c b/lib/asn1/template.c
index 784bfdbc6..42f5c9e6d 100644
--- a/lib/asn1/template.c
+++ b/lib/asn1/template.c
@@ -38,6 +38,7 @@
 #include <vis.h>
 #include <vis-extras.h>
 #include <heimbase.h>
+#include <errno.h>
 
 #ifndef ENOTSUP
 /* Very old MSVC CRTs don't have ENOTSUP */