diff --git a/programs/fuzz/fuzz_pubkey.c b/programs/fuzz/fuzz_pubkey.c
index 95b7521..9e80350 100644
--- a/programs/fuzz/fuzz_pubkey.c
+++ b/programs/fuzz/fuzz_pubkey.c
@@ -60,7 +60,9 @@
         else
 #endif
         {
-            ret = 0;
+            /* The key is valid but is not of a supported type.
+             * This should not happen. */
+            abort( );
         }
     }
     mbedtls_pk_free( &pk );