Index: lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
===================================================================
--- lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -1151,20 +1151,12 @@
     }
     break;
   }
-  // This assert should fire for anything that we don't catch above so we know
-  // to fix any issues we run into.
-  if (!type_name.empty()) {
-    std::string type_name_str = type_name.str();
-    Host::SystemLog(Host::eSystemLogError,
-                    "error: need to add support for DW_TAG_base_type '%s' "
-                    "encoded with DW_ATE = 0x%x, bit_size = %u\n",
-                    type_name_str.c_str(), dw_ate, bit_size);
-  } else {
-    Host::SystemLog(Host::eSystemLogError, "error: need to add support for "
-                                           "DW_TAG_base_type encoded with "
-                                           "DW_ATE = 0x%x, bit_size = %u\n",
-                    dw_ate, bit_size);
-  }
+
+  Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_TYPES);
+  LLDB_LOG(log,
+           "error: need to add support for DW_TAG_base_type '{0}' "
+           "encoded with DW_ATE = {1:x}, bit_size = {2}\n",
+           type_name, dw_ate, bit_size);
   return CompilerType();
 }
 
Index: lldb/unittests/Symbol/TestTypeSystemClang.cpp
===================================================================
--- lldb/unittests/Symbol/TestTypeSystemClang.cpp
+++ lldb/unittests/Symbol/TestTypeSystemClang.cpp
@@ -13,6 +13,7 @@
 #include "lldb/Core/Declaration.h"
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/HostInfo.h"
+#include "lldb/Utility/Log.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/ExprCXX.h"
@@ -46,6 +47,39 @@
   }
 };
 
+TEST_F(TestTypeSystemClang, FailedGetBuiltinTypeForDWARFEncodingAndBitSize) {
+  // Tests GetBuiltinTypeForDWARFEncodingAndBitSize for unknown types.
+  const int unknown_dwarf_ate_value = 123456;
+  const int size = 123;
+  EXPECT_EQ(m_ast->GetBuiltinTypeForDWARFEncodingAndBitSize(
+                "random_type", unknown_dwarf_ate_value, size),
+            CompilerType());
+}
+
+TEST_F(TestTypeSystemClang, LogFailedGetBuiltinTypeForDWARFEncodingAndBitSize) {
+  // Tests that invalid calls to GetBuiltinTypeForDWARFEncodingAndBitSize end up
+  // in the LLDB log.
+  std::string log_output;
+  auto log_stream = std::make_shared<llvm::raw_string_ostream>(log_output);
+
+  std::string error;
+  llvm::raw_string_ostream error_stream(error);
+
+  Log::Initialize();
+  ASSERT_TRUE(Log::EnableLogChannel(log_stream, /*log_options=*/0, "lldb",
+                                    "types", error_stream));
+
+  const int unknown_dwarf_ate_value = 123456;
+  const int size = 123;
+  EXPECT_EQ(m_ast->GetBuiltinTypeForDWARFEncodingAndBitSize(
+                "random_type", unknown_dwarf_ate_value, size),
+            CompilerType());
+  std::string needle =
+      "error: need to add support for DW_TAG_base_type 'random_type' encoded "
+      "with DW_ATE = 0x1e240, bit_size = 123\n\n";
+  ASSERT_EQ(log_output, needle);
+}
+
 TEST_F(TestTypeSystemClang, TestGetBasicTypeFromEnum) {
   clang::ASTContext &context = m_ast->getASTContext();