diff --git a/include/pocketpy/interpreter/vm.hpp b/include/pocketpy/interpreter/vm.hpp
index 07a3f32b..28fc4471 100644
--- a/include/pocketpy/interpreter/vm.hpp
+++ b/include/pocketpy/interpreter/vm.hpp
@@ -465,7 +465,7 @@ public:
     template <typename T>
     Type _find_type_in_cxx_typeid_map() {
         auto it = _cxx_typeid_map.try_get(typeid(T));
-        if(it == nullptr) PK_FATAL_ERROR("T not found in cxx_typeid_map")
+        if(it == nullptr) PK_FATAL_ERROR("T not found in cxx_typeid_map\n")
         return *it;
     }
 
diff --git a/src/common/any.cpp b/src/common/any.cpp
index 6d8558e7..b2274afa 100644
--- a/src/common/any.cpp
+++ b/src/common/any.cpp
@@ -6,7 +6,7 @@
 namespace pkpy {
 
 void any::__bad_any_cast(const std::type_index expected, const std::type_index actual) {
-    PK_FATAL_ERROR("bad_any_cast: expected %s, got %s", expected.name(), actual.name())
+    PK_FATAL_ERROR("bad_any_cast: expected %s, got %s\n", expected.name(), actual.name())
 }
 
 any::any(any&& other) noexcept : data(other.data), _vt(other._vt) {
diff --git a/src/common/memorypool.cpp b/src/common/memorypool.cpp
index 2db6498e..0c82b0ad 100644
--- a/src/common/memorypool.cpp
+++ b/src/common/memorypool.cpp
@@ -287,8 +287,8 @@ void Pools_debug_info(char* buffer, int size) noexcept {
     int arenas = PoolObject._arenas.size();
     // print empty arenas count
     n = snprintf(
-        buffer, size, "PoolObject: %d empty arenas, %d total arenas\n",
-        empty_arenas, arenas + empty_arenas
+        buffer, size, "PoolObject: %d empty arenas, %d arenas\n",
+        empty_arenas, arenas
     );
     buffer += n; size -= n;
     // log each non-empty arena
diff --git a/src/common/str.cpp b/src/common/str.cpp
index 90664be1..fed8827a 100644
--- a/src/common/str.cpp
+++ b/src/common/str.cpp
@@ -16,7 +16,7 @@ int utf8len(unsigned char c, bool suppress) {
     if((c & 0b11111000) == 0b11110000) return 4;
     if((c & 0b11111100) == 0b11111000) return 5;
     if((c & 0b11111110) == 0b11111100) return 6;
-    if(!suppress) PK_FATAL_ERROR("invalid utf8 char")
+    if(!suppress) PK_FATAL_ERROR("invalid utf8 char\n")
     return 0;
 }
 
@@ -379,7 +379,7 @@ StrName StrName::get(std::string_view s) {
     // generate new index
     // https://github.com/python/cpython/blob/3.12/Objects/dictobject.c#L175
     uint16_t index = ((_pesudo_random_index * 5) + 1) & 65535;
-    if(index == 0) PK_FATAL_ERROR("StrName index overflow")
+    if(index == 0) PK_FATAL_ERROR("StrName index overflow\n")
     auto res = _r_interned().emplace(index, s);
     assert(res.second);
     s = std::string_view(res.first->second);
diff --git a/src/compiler/expr.cpp b/src/compiler/expr.cpp
index 92a80753..ed0d38ce 100644
--- a/src/compiler/expr.cpp
+++ b/src/compiler/expr.cpp
@@ -764,7 +764,7 @@ void BinaryExpr::emit_(CodeEmitContext* ctx) {
         case TK("^"): ctx->emit_(OP_BITWISE_XOR, BC_NOARG, line); break;
 
         case TK("@"): ctx->emit_(OP_BINARY_MATMUL, BC_NOARG, line); break;
-        default: assert(false);
+        default: PK_FATAL_ERROR("unknown binary operator: %s\n", TK_STR(op));
     }
 
     for(int i: jmps)
diff --git a/src/objects/namedict.cpp b/src/objects/namedict.cpp
index 0c8ea422..e60a0390 100644
--- a/src/objects/namedict.cpp
+++ b/src/objects/namedict.cpp
@@ -116,7 +116,7 @@ bool NameDict::contains(StrName key) const {
 
 PyVar NameDict::operator[] (StrName key) const {
     PyVar* val = try_get_2_likely_found(key);
-    if(val == nullptr) PK_FATAL_ERROR("NameDict key not found: %s", key.escape().c_str())
+    if(val == nullptr) PK_FATAL_ERROR("NameDict key not found: %s\n", key.escape().c_str())
     return *val;
 }