diff --git a/core/metacling/src/TCling.cxx b/core/metacling/src/TCling.cxx
index 904b85242bc9d..a8df36467e8c1 100644
--- a/core/metacling/src/TCling.cxx
+++ b/core/metacling/src/TCling.cxx
@@ -2663,7 +2663,7 @@ Longptr_t TCling::ProcessLine(const char* line, EErrorCode* error/*=0*/)
                code += codeline + "\n";
             }
             unnamedMacroOpenCurly
-              = cling::utils::isUnnamedMacro(code, fInterpreter->getCI()->getLangOpts());
+              = cling::utils::isUnnamedMacro(code, fInterpreter->getCI()->getSourceManager(), fInterpreter->getCI()->getPreprocessor());
          }
 
          fCurExecutingMacros.push_back(fname);
diff --git a/interpreter/cling/include/cling/Utils/SourceNormalization.h b/interpreter/cling/include/cling/Utils/SourceNormalization.h
index dde8cb326cba0..8a5e5a9a752ec 100644
--- a/interpreter/cling/include/cling/Utils/SourceNormalization.h
+++ b/interpreter/cling/include/cling/Utils/SourceNormalization.h
@@ -20,6 +20,7 @@ namespace clang {
   class LangOptions;
   class SourceLocation;
   class SourceManager;
+  class Preprocessor;
 }
 
 namespace cling {
@@ -29,6 +30,7 @@ namespace utils {
   /// Unnamed macros contain no function definition, but "prompt-style" code
   /// surrounded by a set of curly braces.
   ///
+  /// \note Preprocessing macros are ignored
   /// \param source The source code to analyze.
   /// \param LangOpts - LangOptions to use for lexing.
   /// \return the position of the unnamed macro's opening '{'; or
@@ -36,6 +38,20 @@ namespace utils {
   size_t isUnnamedMacro(llvm::StringRef source,
                         clang::LangOptions& LangOpts);
 
+  ///\brief Determine whether the source is an unnamed macro.
+  ///
+  /// Unnamed macros contain no function definition, but "prompt-style" code
+  /// surrounded by a set of curly braces.
+  ///
+  /// \note Preprocessing macros are fully evaluated
+  /// \param source The source code to analyze.
+  /// \param sm - source manager to use for lexing.
+  /// \param pp - preprocessor to use for lexing.
+  /// \return the position of the unnamed macro's opening '{'; or
+  ///         std::string::npos if this is not an unnamed macro.
+  size_t isUnnamedMacro(llvm::StringRef source, clang::SourceManager& sm,
+                        clang::Preprocessor& pp);
+
   ///\brief Determine whether the source needs to be moved into a function.
   ///
   /// If so, move possible includes directives out of the future body of the
diff --git a/interpreter/cling/lib/MetaProcessor/MetaProcessor.cpp b/interpreter/cling/lib/MetaProcessor/MetaProcessor.cpp
index 701c5555998f0..555a52dc686ca 100644
--- a/interpreter/cling/lib/MetaProcessor/MetaProcessor.cpp
+++ b/interpreter/cling/lib/MetaProcessor/MetaProcessor.cpp
@@ -433,12 +433,12 @@ namespace cling {
     }
 
     if (posOpenCurly != (size_t)-1 && !content.empty()) {
-      assert(content[posOpenCurly] == '{'
-             && "No curly at claimed position of opening curly!");
+      assert(posOpenCurly < content.length() && content[posOpenCurly] == '{' &&
+             "No curly at claimed position of opening curly!");
       // hide the curly brace:
       content[posOpenCurly] = ' ';
       // and the matching closing '}'
-      size_t posCloseCurly = content.find_last_not_of(whitespace);
+      size_t posCloseCurly = content.find_last_not_of(whitespace); // TODO replace instead with preprocessed one, isUnnamedMacro should return tuple start and stop, rather than researching here 
       if (posCloseCurly != std::string::npos) {
         if (content[posCloseCurly] == ';' && content[posCloseCurly-1] == '}') {
           content[posCloseCurly--] = ' '; // replace ';' and enter next if
diff --git a/interpreter/cling/lib/Utils/SourceNormalization.cpp b/interpreter/cling/lib/Utils/SourceNormalization.cpp
index c2f1251d1946e..6e95a8e251ace 100644
--- a/interpreter/cling/lib/Utils/SourceNormalization.cpp
+++ b/interpreter/cling/lib/Utils/SourceNormalization.cpp
@@ -12,6 +12,7 @@
 #include "clang/Basic/LangOptions.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
+#include "clang/Lex/Preprocessor.h"
 
 #include <utility>
 
@@ -443,7 +444,28 @@ cling::utils::isUnnamedMacro(llvm::StringRef source,
   return std::string::npos;
 }
 
-
+size_t cling::utils::isUnnamedMacro(llvm::StringRef source,
+                                    clang::SourceManager& sm,
+                                    clang::Preprocessor& pp) {
+  std::unique_ptr<llvm::MemoryBuffer> buf =
+      llvm::MemoryBuffer::getMemBufferCopy(source,
+                                           "unnamed_macro_candidate_buffer");
+  clang::FileID fid = sm.createFileID(std::move(buf));
+  pp.EnterSourceFile(fid, nullptr, clang::SourceLocation());
+  clang::Token tok;
+  do {
+    pp.Lex(tok); // Lexes while expanding macros and skipping false #if paths
+                 // automatically
+    if (tok.is(tok::comment))
+      continue; // ignore comments
+    if (tok.is(tok::l_brace)) {
+      return sm.getFileOffset(sm.getFileLoc(tok.getLocation()));
+    } else {
+      return std::string::npos;
+    }
+  } while (tok.isNot(tok::eof));
+  return std::string::npos;
+}
 
 size_t cling::utils::getWrapPoint(std::string& source,
                                   const clang::LangOptions& LangOpts) {