diff --git a/src/libstrongswan/crypto/proposal/proposal.c b/src/libstrongswan/crypto/proposal/proposal.c
index c80aa37ef..f88f58ff1 100644
--- a/src/libstrongswan/crypto/proposal/proposal.c
+++ b/src/libstrongswan/crypto/proposal/proposal.c
@@ -37,6 +37,14 @@ ENUM(protocol_id_names, PROTO_NONE, PROTO_IPCOMP,
 	"IPCOMP",
 );
 
+ENUM(protocol_id_lower_names, PROTO_NONE, PROTO_IPCOMP,
+	"none",
+	"ike",
+	"ah",
+	"esp",
+	"ipcomp",
+);
+
 typedef struct private_proposal_t private_proposal_t;
 
 /**
diff --git a/src/libstrongswan/crypto/proposal/proposal.h b/src/libstrongswan/crypto/proposal/proposal.h
index 1005ed0a8..cbb45309f 100644
--- a/src/libstrongswan/crypto/proposal/proposal.h
+++ b/src/libstrongswan/crypto/proposal/proposal.h
@@ -53,6 +53,11 @@ enum protocol_id_t {
  */
 extern enum_name_t *protocol_id_names;
 
+/**
+ * lower case enum names for protocol_id_t
+ */
+extern enum_name_t *protocol_id_lower_names;
+
 /**
  * Flags for selecting proposals.
  */