diff --git a/oscar64/Errors.cpp b/oscar64/Errors.cpp
index ff29cf5..5522e47 100644
--- a/oscar64/Errors.cpp
+++ b/oscar64/Errors.cpp
@@ -35,7 +35,7 @@ void Errors::Error(const Location& loc, ErrorID eid, const char* msg, const char
 	else
 		fprintf(stderr, "%s(%d, %d) : %s %d: %s\n", loc.mFileName, loc.mLine, loc.mColumn, level, eid, msg);
 
-	if (mErrorCount > 10)
+	if (mErrorCount > 10 || eid >= EFATAL_GENERIC)
 		exit(20);
 }
 
diff --git a/oscar64/Errors.h b/oscar64/Errors.h
index dcf4a97..967cf6c 100644
--- a/oscar64/Errors.h
+++ b/oscar64/Errors.h
@@ -36,7 +36,6 @@ enum ErrorID
 	EERR_RUNTIME_CODE,
 	EERR_UNIMPLEMENTED,
 	EERR_COMMAND_LINE,
-	EERR_OUT_OF_MEMORY,
 	EERR_OBJECT_NOT_FOUND,
 	EERR_SYNTAX,
 	EERR_EXECUTION_FAILED,
@@ -86,6 +85,10 @@ enum ErrorID
 	ERRR_INVALID_NUMBER,
 
 	EERR_INVALID_PREPROCESSOR,
+
+	EFATAL_GENERIC = 4000,
+	EFATAL_OUT_OF_MEMORY,
+	EFATAL_MACRO_EXPANSION_DEPTH,
 };
 
 class Errors
diff --git a/oscar64/Scanner.cpp b/oscar64/Scanner.cpp
index 535736b..c1541d6 100644
--- a/oscar64/Scanner.cpp
+++ b/oscar64/Scanner.cpp
@@ -318,6 +318,7 @@ Scanner::Scanner(Errors* errors, Preprocessor* preprocessor)
 	mAssemblerMode = false;
 	mPreprocessorMode = false;
 	mMacroExpansion = nullptr;
+	mMacroExpansionDepth = 0;
 
 	mDefines = new MacroDict();
 	mDefineArguments = nullptr;
@@ -817,6 +818,9 @@ void Scanner::NextToken(void)
 				ex->mChar = mTokenChar;
 
 				mMacroExpansion = ex;
+				mMacroExpansionDepth++;
+				if (mMacroExpansionDepth > 1024)
+					mErrors->Error(mLocation, EFATAL_MACRO_EXPANSION_DEPTH, "Maximum macro expansion depth exceeded", mTokenIdent);
 				mLine = def->mString;
 				mOffset = 0;
 				NextChar();
@@ -1812,6 +1816,8 @@ bool Scanner::NextChar(void)
 
 			delete mMacroExpansion;
 			mMacroExpansion = mac;
+			mMacroExpansionDepth--;
+
 			return true;
 		}
 		else if (mPreprocessor->NextLine())
diff --git a/oscar64/Scanner.h b/oscar64/Scanner.h
index 51d8b0a..2c61d7d 100644
--- a/oscar64/Scanner.h
+++ b/oscar64/Scanner.h
@@ -259,6 +259,8 @@ protected:
 		MacroDict* mDefinedArguments;
 	}	*	mMacroExpansion;
 
+	int			mMacroExpansionDepth;
+
 	MacroDict* mDefines, * mDefineArguments;
 
 	Token		mUngetToken;