diff --git a/src/libcharon/config/proposal.c b/src/libcharon/config/proposal.c
index 698ff40d3..e1305ce91 100644
--- a/src/libcharon/config/proposal.c
+++ b/src/libcharon/config/proposal.c
@@ -958,9 +958,12 @@ static bool proposal_add_supported_ike(private_proposal_t *this, bool aead)
 			case MODP_768_BIT:
 				/* weak */
 				break;
-			case MODP_2048_224:
-			case MODP_1536_BIT:
 			case MODP_1024_160:
+			case MODP_2048_224:
+			case MODP_2048_256:
+				/* RFC 5114 primes are of questionable source */
+				break;
+			case MODP_1536_BIT:
 			case ECP_224_BIT:
 			case ECP_224_BP:
 			case ECP_192_BIT:
@@ -968,7 +971,6 @@ static bool proposal_add_supported_ike(private_proposal_t *this, bool aead)
 				/* rarely used */
 				break;
 			case MODP_2048_BIT:
-			case MODP_2048_256:
 			case MODP_1024_BIT:
 				add_algorithm(this, DIFFIE_HELLMAN_GROUP, group, 0);
 				break;