diff --git a/cql3/constants.cc b/cql3/constants.cc
index aef6f39cf9..f757b992d1 100644
--- a/cql3/constants.cc
+++ b/cql3/constants.cc
@@ -61,6 +61,7 @@ operator<<(std::ostream&out, constants::type t)
         case constants::type::DURATION: return out << "DURATION";
     };
     assert(0);
+    return out << "UNKOWN";
 }
 
 bytes
diff --git a/db/schema_tables.cc b/db/schema_tables.cc
index bc556cbe0e..17b08c092c 100644
--- a/db/schema_tables.cc
+++ b/db/schema_tables.cc
@@ -620,6 +620,7 @@ future<mutation> query_partition_mutation(service::storage_proxy& proxy,
                         return partitions[0].mut().unfreeze(s);
                     } else {
                         assert(false && "Results must have at most one partition");
+                        throw std::invalid_argument("Results must have at most one partition");
                     }
                 });
     });
diff --git a/dht/byte_ordered_partitioner.cc b/dht/byte_ordered_partitioner.cc
index a5e34eff1f..5bad539904 100644
--- a/dht/byte_ordered_partitioner.cc
+++ b/dht/byte_ordered_partitioner.cc
@@ -160,6 +160,7 @@ byte_ordered_partitioner::shard_of(const token& t) const {
             return (uint8_t(t._data[0]) * _shard_count) >> 8;
     }
     assert(0);
+    throw std::invalid_argument("invalid token");
 }
 
 token
@@ -177,6 +178,7 @@ byte_ordered_partitioner::token_for_next_shard(const token& t, shard_id shard, u
         return token(token::kind::key, managed_bytes({int8_t(e)}));
     }
     assert(0);
+    throw std::invalid_argument("invalid token");
 }
 
 
diff --git a/dht/murmur3_partitioner.cc b/dht/murmur3_partitioner.cc
index ca4a0a7803..5684ee9fc5 100644
--- a/dht/murmur3_partitioner.cc
+++ b/dht/murmur3_partitioner.cc
@@ -255,6 +255,7 @@ murmur3_partitioner::shard_of(const token& t) const {
             return zero_based_shard_of(adjusted, _shard_count, _sharding_ignore_msb_bits);
     }
     assert(0);
+    throw std::invalid_argument("invalid token");
 }
 
 token
diff --git a/dht/random_partitioner.cc b/dht/random_partitioner.cc
index ec5d261cd9..19715778c1 100644
--- a/dht/random_partitioner.cc
+++ b/dht/random_partitioner.cc
@@ -220,6 +220,7 @@ unsigned random_partitioner::shard_of(const token& t) const {
             return smp;
     }
     assert(0);
+    throw std::invalid_argument("invalid token");
 }
 
 token
@@ -240,6 +241,7 @@ random_partitioner::token_for_next_shard(const token& t, shard_id shard, unsigne
             return cppint_to_token(t.convert_to<boost::multiprecision::uint128_t>());
     }
     assert(0);
+    throw std::invalid_argument("invalid token");
 }
 
 
diff --git a/position_in_partition.hh b/position_in_partition.hh
index 765a1a73a6..2b60a26511 100644
--- a/position_in_partition.hh
+++ b/position_in_partition.hh
@@ -36,6 +36,7 @@ lexicographical_relation relation_for_lower_bound(composite_view v) {
             return lexicographical_relation::after_all_prefixed;
         default:
             assert(0);
+            throw std::invalid_argument("invalid composite_view");
     }
 }
 
diff --git a/schema_registry.cc b/schema_registry.cc
index dd0a12cf1b..2bdee0c02e 100644
--- a/schema_registry.cc
+++ b/schema_registry.cc
@@ -235,6 +235,7 @@ future<> schema_registry_entry::maybe_sync(std::function<future<>()> syncer) {
         }
         default:
             assert(0);
+            throw std::logic_error("invalid _sync_state");
     }
 }
 
diff --git a/sstables/compress.hh b/sstables/compress.hh
index 22d3025999..d2f9d40e24 100644
--- a/sstables/compress.hh
+++ b/sstables/compress.hh
@@ -177,6 +177,7 @@ struct compression {
             const_iterator& operator=(const const_iterator& other) {
                 assert(&_offsets == &other._offsets);
                 _index = other._index;
+                return *this;
             }
 
             const_iterator operator++(int) {
diff --git a/unimplemented.cc b/unimplemented.cc
index 2a11b1b9de..23e7373312 100644
--- a/unimplemented.cc
+++ b/unimplemented.cc
@@ -64,6 +64,7 @@ std::ostream& operator<<(std::ostream& out, cause c) {
         case cause::VIEWS: return out << "MATERIALIZED_VIEWS";
     }
     assert(0);
+    return out << "UNKNOWN_CAUSE";
 }
 
 void warn(cause c) {